These types of historical HC decisions read nice, fill the page and make you feel better about paying for a subscription service (dunno if this was free or not), but the situations are not the same. Rice in 2008 was playing behind McGahee, a legit vet back. This would be akin to the Demarco Murray, Henry situation, or C.J. and Booker if C.J. never got injured. I wouldn't glean to much insight from that 4for4 article, although I do respect their work.
Ray Rice owned the position until the latter half of 2013 and no rookie RBs existed for BAL to take his spot when he got the boot. 2014 Forsett broke out. So while it sounds like in 8 years history proves that Harbaugh won't play rookies more than X amount of carries per game, it really came down to BAL already having a capable vet back during Rice's rookie year AND them sticking with Rice until 2014. Forsett filled in nicely as a vet back in 2014 and the first part of 2015. So really there was only one year where an opportunity existed to play a rookie back and that was 2nd half of 2015 after Forsett went down. Have you seen their rookie RBs from 2015? JAG city, which is why they drafted a stud in 2016. The story is a non-factor and means nothing. It would probably had served your Dixon decision better if you had never read it.
What's more important info is that Dixon was getting groomed to be the starter during his pre-season breakout, and they waived Forsett even after his injury. Forsett was the only sentimental thing in his way. West has been on the team only a little while longed than Dixon and is not a huge road block.