See https://stackoverflow.com/questions/65757640/has-optaplanners-tolist-constraintcollector-a-bug

The issue is in the underlying Drools executable model. `createVariable(..., from(accumulateResult))` works well when `accumulateResult` is a single thing. If it's a collection, it starts giving results one by one, and not the list as a whole.

Pretty sure this is a regression, it worked in the past.