To clarify at:alternate vs at:event (I did not do a good job in the original post) the difference to me would be:
at:alternatewitheventrecord ⇒ the page represents the event itselfat:event⇒ the event is mentioned in the page, but is not the subject of the page (think a blogpost that’s promoting an event or was made as part of it).
That said, I would (personally) leave honing in on the full semantic to a side thread once people agree on the general direction. That seems an even longer discussion to have 