PLO raise size question

I saw this situation come up in a recent WSOP stream but I think the the rule would be the same in a cash game.

Blinds are 150/300k. MP player opens pot for 1.05M. SB announces raise and asks the dealer the minimum amount. Dealer says 2.1M which of course is double the bet.

Is that correct? In NL the minimum would be 1.8M (since the original raise was 750k over the 300k). So a click back minimum would be 1.05M + 750k = 1.8M.

Am I missing something in the mechanics or is there a rule in PLO for min raises that differs from NL? I was scratching my head cuz it felt like the dealer got this wrong but the players let it go and proceeded with no issue raised.

Thanks