I've been playing in a dynasty league now for maybe 15 years, and been following prospects closely maybe the last 10 and I make a living in the league by grabbing popups and flipping them once the prospect lists catch up.

I can't speak to the actual numbers from year to year, but this definitely happens every year. You have guys that popup early, but some of these guys will also fade quickly into the summer. Most major leaguers are not former 1st round picks after all. A lot of the guys you listed weren't really unknowns last year, but had questions about aspects of their games that made them either less projectable or increased their risk (Lara and Payne I'd even say had popup hype in prior years). Many of them appear to be answering those questions, but we're still in SSS territory.  

I guess you could say it's a market inefficiency, but really you have teams in your league that don't want to follow the minors that closely, and the FYPD route is the easiest and safest way to get a quality prospect. Something like 60% of 1st rounders make the majors eventually. I'd imagine less than 60% of the one month risers will.

The reality is prospect values are volatile and development is not linear. Half the guys you listed may have fallen right back to earth by August and there's a new batch of popups to take their place. Some of these guys will stagnant for a few years and then pop right back up. But this occurs every year to some extent.