That part I find a bit hard to swallow. They send the owner the names, physical address, email address, and cell phone number of every person to be included on the reservation, and they do that for every one of hundreds and hundreds of rentals. There's zero chance that this hasn't happened before.
You can see how easily an owner could try to do what your owner did and cut out the middle man. I could also see an owner, actually just trying to help a renter, directly contacting that renter to figure out reservation changes, adding or removing guests, adding the dining plan, etc. instead of having to go through the third party multiple times. Especially in light of the $50 per change charge that DVCRS will tack on.
Again, I totally agree with you that it shouldn't have happened, but the pearl clutching by DVCRS might be a bit much. I'm curious why she didn't straight out lead with "we have a strict policy against that".