The police are not actively looking for your phone. You are. If they ever coincidentally come across a hoard of stolen phones they will check IMEI numbers. If one or more of the phones shows lock mode with contact details to the legitimate owner, their job becomes easier. This is a small chance, but a chance nevertheless.

If you release the phone from FindMy & reset it, the thief can then re-sell it, untraceably & in full working order. The new owner, though in possession of stolen property, will never know.
Bye bye phone for ever.