Dorico-Quick-Look-Extension-Mac using more Memory than Dorico opened

Using MacBook Pro M1 Max 64GB - Sequoia 15.3 - Dorico 5.1.81

Is that correct?

I don’t think that should be expected.
On my end, I had a few crashes of that component in the last week.
I suggest saving your work, manually quitting Dorico and see if it goes away.
If it doesn’t, then the process may be stuck and could require manually quitting or force-quitting it.

A simpler way could be to log-out of macOS and log back in, or restart the Mac entirely.