Exactly. The problem with this example is that it's not an all or nothing proposition. Uniqueness, IMO, isn't a good thing or a bad thing. Our teams are unique enough or will become so as you move down to the final 250. there is no need to purposely seek out additional uniqueness.
Where you fall on uniqueness partially goes back to your philosophy for this contest. I believe in doing what's best for the first 13 weeks, and taking my chances in the final 3 weeks, so I tend to believe that uniqueness is an unimportant consideration. If you fall on the other side of the former debate, then you may also align with those who believe uniqueness is important.
I'll start by saying I believe it's probably true that, all else being equal, it's better to be more unique than less unique in the final 250, if your goal is to win the grand prize. This is similar to the idea that small rosters are better because they exhibit greater variance - with a more unique team, you're more likely to end up at the extreme ends of the final standings. You're either going to be near the top, or near the bottom. With a less unique team, you may be more likely to finish in the money, maybe in the top 50, but less likely to be the #1 overall team. I don't know if that's actually true, but it's my intuition. This is where the earlier coin flipping example is somewhat appropriate - if everyone picks heads, they'll all be huddled around each other in the standings, so to speak; if you go against the grain and pick tails, then you're either going to win the thing right away or lose right away. From a contest perspective, if you only care about winning the $20,000, and have no interest in winning $25-50 for coming in the top 100 or whatever, then uniqueness is probably your friend. I think most people probably fall in this boat.
But as with many other contest discussions we've had in the past, we need to remember what we do and don't control. You don't get to pick a new lineup leading in to week 14. You have to make your selections in August. While it's occasionally obvious that some players will have relatively high ownership percentages (Benson this year, Foster a couple years ago, etc.), for the most part you don't actually know how heavily owned a player will be. Furthermore, unlike the hypotheticals that are often presented in this debate, it's never actually the case that 99.9% of the teams own Player A, and you're the only team with Player B, at least not in August when you're making your picks. It's both far more complex and unpredictable than that.
The fact is, as I've said here before, some teams are more unique than others, depending on how you define such a metric, but all teams are
sufficiently unique to win the contest. There are no duplicates. There are no rosters that are completely covered by others. You need to put up a string of 200 point weeks in the end - if your players do this, you'll finish near the top. If they don't, you won't. Whether or not they do score that many points for you is independent of how commonly owned they are. Darren Sproles won't be sitting on the sidelines in week 14, checking how many teams still own him in the contest before he decides whether or not to go off for 50 points that week. Besides, if there is a correlation, I'd suspect that the more commonly-owned players are more likely to score a ton of points, since they presumably carried more teams to the final 250, and have therefore been better players during the season. I said uniqueness is good,
all else being equal, but all else isn't equal. If Player A wound up on most of the final 250 teams, he must be a pretty good player. He may in fact be more likely to put up a ton of points than Player B who's only on a handful of final 250 rosters - not because he's on more rosters, of course, but simply because he's a better player that year.
Similarly, at the outset of the contest, the most commonly-owned players probably present the greatest value ("wisdom of the crowds" and all that). If everyone identified $3 Benson as the player most likely to outperform his price this year, what does it say about the entries that don't have him? The goal is to load up on as many players that will vastly outperform their price as possible - Benson is the prime example this year, and if you agree, why would you leave him off just to be more "unique?" You'd just be shooting yourself in the foot by intentionally passing on a guy who has the exact attributes you should be looking for.
So when people argue about whether or not uniqueness is good in the final 250, they may be right, but it's sort of uninteresting (to me, at least) because that's something you have pretty much no control over. All of the really good strategy discussion that has taken place over the years deals with the things we do have control over - roster size, budget allocation, bye week strategies, etc. Uniqueness in the final 250 falls pretty far outside that scope. Build your roster with the intention of scoring the most points you can, and let the uniqueness part of it sort itself out.