It's still possible to recover lost gmail for as long as the number is saved and he can go to his service provider trying to ask that number of his by verifying through his IDs.
I believe that this is possible for most countries and you can retrieve the number first if registered in the provider before recovering the email. But even without the number, there could be some secret questions that have been set on that gmail that only he can answer if he ask gmail for retrieval.
It seems you're right. Well, before it was not recoverable, but right now here in my country, it seems it's possible to report this and request a replacement.
It needs an affidavit notarized and 2 valid IDs, but I don't think you can recover it if the SIM card isn't registered in your name.
If OP is verified with his name, the chances of recovering and replacing a similar SIM number are possible, which can be used to recover both the Gmail and Binance accounts.