If you mean like how they randomly learn new stuff like Hado 108 or BJK, I'd say that's more because Seigaku guys start out with very lousy moveset so they got to pirate other people's moves to have a shot.
everyone as a whole, except for a few like fuji , and golden pair copied or added anothers moves to their special moves.
on the one hand you can call them sucky for borrowing other's techniques, but some made them better and more powerful.
Momoshiro however, was original up until BJK.
The Jack Knife we only saw Atobe use, after we saw Momoshiro use it.
Bullet Serve, which doesn't even effect Bottom Tier players (The Dane-guy from St.Rudolph and the twin with the red headband handled it and they are bottom tier).
Kawamura is a perfect example though. Totally copied the degrees of Hadoukyuu and mastered it.
Ryoma's copying is different since that was part of the plot for Konomi. To have him go from copying to being the best in his own right.
Tezuka doesn't copy at all. Zone, Phantom, Zero Shiki, all shots that he pioneered. You immediately think Tezuka when you see them being used. Tezuka is an original full stop. HJnK is just a move that reflects.
Kaidoh was completely original until Gyro Laser too. Snake is totally his thing. However now he is just the same as Yagyuu. Their biggest threat is that they hit more than one shot from the exact same stance making them impossible to predict.
Fuji is an original. No discussion needed.
Kikumaru isn't necessarily original but it's not he and Mukahi copied one another so they're fine. To help Eiji, Kikumaru is an much better version of Mukahi. Kikumaru has Seal Step and Bazooka.
Oishi sucks in Singles for now. But his Doubles abilities are original.
Inui was taught by Yanagi so you can argue that for him.
All in all, Seigaku don't copy too much.
They are all, in fact, copycats. Except for Fuji, though, because his Triple Counters were the original techniques that garnered him the title of "Genius." Seigaku's as OP as it gets when it comes to copycats, really. Except for Kaidoh.
Buggy whip shot?