Shares aren't that. They're just proof that you did some work, that is just solving a block at an arbitrary difficulty.

You aren't given more shares for getting "closer" to the correct answer, but if you're given a higher difficulty target (appropriate for more powerful machines) then your shares will be worth more than other shares. BUT pools will always normalize this on the website/stats so you don't have to do any adjustment.

So you're kind of right but that's only of concern to the pool back end.

In reality a bitaxe share and a S21 Pro share are going to be worth the same, it's just that the S21 will be finding them way faster, be given a higher difficulty target by the pool, then return fewer shares that are worth more than previously. So if you double the difficulty you send to a worker, each share it submits will be worth two shares.