Some more examples of "non-modules":
https://modulargrid.net/e/intellijel-4u-x-62hp-palette-case-top-row-silver-0-5u
There are more similar entries for Intellijel case top rows, looks like 4 ones that I looked at combined are used in over 12000 racks.
Make Noise 0-coast, used in 4500 racks:
https://modulargrid.net/e/make-noise-0-coast-
Make Noise 1u cv bus, used in 4400 racks:
https://modulargrid.net/e/make-noise-cv-bus-case
Looks like quite a lot of people seem to like using "non-modules" in their racks. Personally, I don't see a problem with any of the examples I know of.