Please consider adding “Show Album as Calendar Event” - just like you’ve already done for Folders. When enabled, the Event would show up on the Calendar - but would be scoped only to photos included in that Album.
I think it would be especially useful since many people already use the terms Albums and Events interchangeably. Ask what is an Album? Often the answer is - it’s a curated set of photos from a specific Event.
This would also give users an easy way to “manually” add photos to an Event - just add them to that Album. A much more straightforward method than trying to finesse some metadata as Event Filter criteria.