Someone left the bath running... that's what the overflow drain is for http://www.freediyhomeimprovement.com/wp-content/uploads/201...
The rest is bad on Airbnb though.
The rest is bad on Airbnb though.
Edit: Two other notes. 1) The age is irrelevant, even some Victorian-era claw foot tub would have an overflow. 2) I can imagine a scenario where the drain itself is hairclogged at the tailpiece such that it is draining slower than the tub is filling, thus potential overflow.
Edit: From Sharon's video, a trip-level stopper/overflow plate: https://youtu.be/CKuTdZ5T8Ao?t=138