So your logic for not being allowed to charge the same price on itch and steam is invalid. VAT is not applicable to most customers.
I don't know why you're arguing from a place of complete ignorance. Read the section on rules, number 4 and then please tell me the magic spell I can cast to make the world you want a reality.
Since you asked me, I don't see the issue with the rule. Steam does not want you to charge a higher price than what is offered on other sites. You specifically stated that itch will add tax/vac to the price, but Steam will not. So if you make the prices $4.99 on both sites than itch may be a higher price, which is exactly what Steam wants. Steam gets the lower price. No magic spell needed.