I think the sibling post by samwillis explains my view the clearest.

Basically, the business case for breaking the signup flow to require users to check their email is low. It interrupts flow and reduces conversion rates.

The suggestion then is yes, you are allowed to use emails you don't own to sign up for an account. The reason this is allowable is that who would want to do it? The account would be broken and the real owner of that account can pop your password.