hello there! there are not many presses on modern gymnastic. practically every move is done with straight arms. And i don't remember doing slow press as a body-conditioning, but again, i'm talking the 80s here when i used to compete.
i've seen videos of guys backwards rolling and popping out fast, but never in a deliberately slow manner. would this press help develop a full HSPU?
from my point of view...Yes indeed!!!
all the best