About SHA1 in default Disk Encryption in Linux

Link to the Thread:

Recommended options for LUKS (cryptsetup)

I wonder what's the exact difference between SHA1 and SHA512. I know that SHA512 has a longer key but I've read that it doesn't matter which one you chose because LUKS loops the Hash until 1 second real time has passed.

So why are there even the options to SHA512, Whirlpool or SHA56? What is the difference? Seems like there isn't. I'm a bit confused.

Regards