I would prefer a checkbox in ‘Preferences’ and a button for a high quality preview on demand, for which functionality you should also have a checkbox for DeepPRIME.
In the field I’m using a laptop with i3-10110 CPU (2 cores) and no graphic card,
to generate images for initial selection (with DP off, as it would take some
10 minutes per image). I would hate the extra hiccups during the editing.
Probably the current behavior was introduced long time ago,
due to user requests having this problem.
See also Make sharpening visible at less than 75% zoom - DxO PhotoLab / Feature requests - DxO Forums
There should also be older posts about it somewhere.