Does doing past papers actually help?

This might sound strange but does it really help?
Whenever my school does mocks, they just reuse old past papers. If someone does all past papers (maybe since 2018) and all those questions come up in the mock, aren't you bound to get a nine since you already know what questions to expect? I did that and got three 9s on my first round.
However, I am afraid that if I just do all the past papers, will my actual grade be lower than mocks? I know it sounds kind of strange but I needed to ask someone. Please don't judge, lol.
Thank you >-<

Why my Maths teacher didn't recommend past papers for revision.

Yes it does help - can confirm. It helps you review the material and put the information in the terms the exam board wants, and it helps you understand the structure of the questions you're likely to see.

Lol, it makes sense if they don't but my teachers always bring it up. They also literally tell us it is past paper questions.

Edexcel produce secure mocks for teachers which are far more helpful.