New Season has rolled, looking at player ratings.
Pitcher age 28, gained some points here and there.
I might have read that this happened before, but is this extremely rare?
Will it be given back after Spring Training?
Always thought 27 was last year to gain (if any).

It can happen after 27. You can definitely see it in a DITR even after 27, but you will see it in other players too. I have seen a bump at age 28, 29, or 30. Sometimes though it seems like the player will give it back somewhere the next season.

I have seen that as well, but it always seems to be pitchers for some reason

I've seen it with position players, too, and not DitR... can't remember it in a 29 yo hitter or a 30 yo pitcher. I think, but am not certain, that these players also decline slightly later than is typical.

I've seen players get some decent gains in their late 20s or even early 30s. I've especially seen it in players that came from teams that have poor mlb coaches until their late 20s, then, all of a sudden, they gain two points in eye and 1 in each split during one season on a team with premium coaches. My guess is that the player was likely sitting at or close to the next point and the improved coaching allowed him to reach a bit more potential.