Not sure how you can say my info is 100% false. Perhaps your league has different settings. Perhaps there is a setting that commissioners can make to allow this - though I have not encountered it and I find it hard to believe that Yahoo would ever allow a player to be subbed out after their game has started. Certianly it has NEVER been allowed in any of my leagues in Yahoo dating back 6 or 7 years now. As an example,... TODAY, in the same league in which I am commissioner, I (as owner, not as commissioner) made a last minute substitution as 1pm (EST) approached. I changed my mind as soon as I made the subsitution. Went back in to undo it.... I was not allowed to and received the message... "Transaction not allowed" (or something to that effect). Yahoo showed 1:02pm at the time of that message.
Commish Tools -> Edit rosters. 5 min left in the Q1 of NE/GB, and I, as the commish, went into the league and changed the lineup of 3 different teams. I replaced Finlay, Brees, and Rodgers with players who played earlier today. The lineups and scores are updated, yet there is no timestamp or mention of a roster change.ETA: I also subbed out Gostkowski and there was no message. However, when I subbed Gostkowski out of the week 14 lineup, there was a note that the roster was changed, but it did not say what players were changed. So, if you are in the finals of a Yahoo league, you should take a screenshot of the starting lineups at gametime.