If they tell you to leave, you refuse, and you stay there for the length of time it takes for them to call the cops and for the cops to arrive, you’re committing a crime

I don't think that's necessarily true. There are a fixed number of people who can issue a legally binding trespass order, and it's unclear if your average desk clerk has that authority, since it needs to be issued by the property owner or someone authorized to act on behalf of the owner WRT trespass warnings. So it's completely reasonable IMO to wait for a police officer to investigate whether the person actually has that authority before complying with the trespass order.

That said, if you leave, you may avoid a legally binding trespass order. If you remain, my understanding is that you won't be arrested unless you refuse to leave after receiving the formal trespass warning (and the cop may order you off the property until it's issued). It's safer to wait outside the business than remain inside it, but I would be very surprised if a court would uphold an arrest if you're calmly waiting for the cop to show up and investigate. Yes, you could be arrested, but I doubt that arrest would "stick" on your record, and you may have a case to sue the cop depending on how the arrest was handled.

“warning” they got verbally from the cops 10 seconds ago wasn’t legally sufficient

Yes, when the warning comes from the cops, that's a lawful order, and disobeying it runs a risk of arrest on its own, regardless of the trespass order behind it. That's not this situation, we're talking about a desk clerk at a business threatening to call the cops if you don't leave, and that desk clerk's authority to issue a trespass is suspect.

This is definitely running on the edge of the law and could absolutely change by jurisdiction, but my understanding is that, in the majority of jurisdictions, ignoring a trespass warning from an employee is not an arrestable offense. Obviously, do your own research and/or consult an attorney if you're going to do this on purpose.