Rule 5 Guys like https://www.whatifsports.com/hbd/Pages/Popups/PlayerRatings.aspx?pid=10600328
a rule 5 pick who stays in majors and doesn’t improve on splits: what gives? PT, coaching is there.

Is it just the> 18 IFA thing where they just don’t develop? I think he was 19 at signing.

Ints tend to gain ratings slower / not at all. For Rule V players unless they are diamonds in the rough I don't expect them to gain any ratings points after signing. Typically by year 5, they have hit their max.

Things that slow down and eventually stop development:

1) increasing age - Most player develop very little, if any, after age 24
2) increasing number of pro years - Most players develop very little, if any, after 4 pro years.

The exception is Diamonds in the Rough. They will still show development at age 25 into 26 if they became a DitR a bit older like 22-23. Also show development into pro years 5 and 6 if they became a DitR a bit later like in pro years 3-4.