I understand the seniors have hardly any leverage but now that the multimillion-dollar signing bonuses are no longer available in the lower rounds anymore since each slot has pool money per round and if that kid won't sign for that pool money slot, that team loses that money. So you get kids that come to college out of HS, and older college guys staying in school.

So for players selected in the 11th round and beyond, portions of signing bonuses above $100,000 would count against the bonus pool.

Whether that effects college juniors to stay for their senior year or not , time will be the determining factor. There more juniors coming back these days, than in previous years under the new system.

I would actually disagree. You don't see many top 10 round guys coming back (Helman was 11th round, but got 6th-7th round money). He may have improved his draft position, but it would be highly unlikely he would get more money. Each pick has a slot, but just about every pick is negotiated before it happens. College seniors are often chosen in the top 10 rounds with the understanding they will be signing for pennies on the dollar (ex. $10k for $400k slot) in order to move money to overslot high school and >10 round guys wanting >$100k.

The only player I can name in recent memory that made more money going back as a senior was mark appel who was selected 1-1.

Here's an article from a couple years ago on seniors in the draft...

https://www.forbes.com/sites/darrenheitner/2014/03/30/money-extremely-limited-for-college-seniors-seeking-to-play-professional-baseball/#69c68c547ffa

Selfishly, I would have loved it if he can back, but I don't think that was realistic. Helman was 22 on draft day and would have been 23 for the 2019 draft. He had a really good year last year, and I don't think another year would have increased his prospect value enough to justify turning down the money he got. He probably would have to be viewed as a 1st or 2nd round talent for teams to pay him more than he got.

Shewmake currently ranked 18 on Fangraphs prospect list with a 45FV rating. Both of the Cypress recruits also have FV 45 ratings.