Advice? - Seller name is fake, seller doesn't release BtC

I have made tens of successful BtC purchases so far, with only one issue that was resolved.
However, few days ago I encountered a weird seller. I purchased BtC and sent money via Zelle. In Bisq, the seller used email in name and email fields. When I looked at my Zelle account, the statements says the money was sent to “null, null”. I’m pretty sure this is not a real name. The seller’s account was also 0 (zero) days old (I realized after I sent money).

Are sellers allowed to put these fake names? I haven’t contacted arbitrator - should I open case without delay?

No, traders are required to give their real names. If the seller put his email in the name field, that is against the protocol and you should open a dispute with alt+o.