Can I use 75% alcohol prep pads to sanitize my iPhone 12 Pro Max?

I think Apple just said 70% because that is the most common alcohol wipe, and the one carried by most pharmacies. 75% shouldn’t be a problem. Yours are probably also 75% ethanol, rather that 70% isopropyl. The higher alcohol content also means a lower water content, and it is water that is the real threat in cleaning agents.

But if you want to be surer use the Get Support link at the top of this page and ask.

Cleaning your iPhone - Apple Support

Well, as those are what Apple has on their tables in Apple Stores, I would assume the answer is yes.