Mainly just want to ask just out of curiosity, but are people going to get steam codes if they bought the game here?
Nope, I doubt it.
Steam is a completely different platform, and the definition of a "digital copy" for ExtraLife does not exist yet, so we are not even talking about Cross Platform Sharing.
In that case, the keys would have to be sent manually to each person, and there are not a few of them, and moreover how to know to who send it? I doubt that it is possible to send emails to all customers via Itch.io, and even if it is - w/out any automation, this is not an option.