I became a citizen this month after applying back when we still had a Queen and I got tripped up when saying the oath due to this---I'm on my 30s, there's been a Queen forever, I'm not used to having a King.
I'm sure I'll get used to it at some point but man that felt weird.
Pretty much the same for me. The citizenship test booklet I used hadn't been updated yet, even though it was a fair bit after she'd passed. And in the ceremony, it was all about the king.
(Not to mention that it's super weird to affirm your allegiance to a monarch no matter what...)