A list could also have been effectively re-constructed by investigators by identifying names in documents, faces in videos, financial transactions, and cell phone records. But who runs any kind of business or operation without having some kind of customer management system, even if but a crude form of one?
Only if investigators actually wanted to do so.
I'm more of the opinion that any lists that exist(ed) outside of Maxwell have been actively used blackmail material by the deep staters. The FBI files have been in the possession of the Rats for 4 years. Who could possibly believe they haven't been seriously monkeyed with? I don't know that I'd believe anything in them after the Rats have had them for so long.