There’s a lot of things to learn from Rittenhouse, anything about the forward assist is much further down the list vs tactics, techniques, and procedures.
Had Rittenhouse used a better quality AR15, better magazines, and better ammunition his use of the Forward Assist very likely may not have been necessary. Had he used it more prior to this incident and done better maintenance it may not have been necessary.
Training for the firearm to be fired off the shoulder, held weakly, or fired from the supine position, would reveal if it can actually run under those conditions. Not all AR15s can.
Having watched most of the trial as it aired far more relevant lessons;
1) Showing up to an active conflict zone with only one person you know and trust is not a good idea.
2) leaving the private property you are guarding is is both tactically and legally unsound.
3) running around doing every “side quest” is tactically and legally unsound.
4) doing the same alone and unsupported is even more tactically unsound.
5) not having a clear leader of the security force lead to everyone there acting independently
All of the above lead to the situation where he was alone, unsupported, and targeted by hostile actors.
He did exercise better shoot/no-shoot decisions under stress and while having his bell rung than most cops would, so props for that.
He is very lucky he survived the situation, and he is also very fortunate he survived in court.
There are more things to consider from the incident and their preparation going into it, but these are the things I easily remember 6 months after watching the trial, the video evidence, and the testimony.
So if what you got out of the Rittenhouse case is that the forward assist saved his life, you’re missing the forest for the trees.