The way constraints are updated using the old updater is suboptimal and partial:
- does not take the revision into account
- only fetched on item edits
- they all disappear after a data-reload
- the new streaming updater does not support these
- user impact does seem small: 370 out of 230,492,864 queries for jan 2021 are using the wikibase:hasViolationForConstraint predicate
I suggest to disable them while a proper solution is found and put in place on the wikibase side (T201150, T201147)