I can answer that:
1) The IRS loves SSN because it is the easiest way to track people, once you have it you need to use it all the time.
2) EIN is for business yes but what i think the IRS thought is that you do not have anyway to do business. I do not know it is tricky but not important or something to worry about because...
3) Once you have someone you do need a EIN this helps IRS not track you, its like an easier way to keep things in order.
4) I think you need to ask itch.io support if any changes is needed for taxes.
another website can explain this in full detail if you are still confuse: https://www.nolo.com/legal-encyclopedia/ein-employer-id-number-for-business-3612...