I only briefly emailed with two agencies months ago. I know for certain, one of them required login level access. If that changed from summer of last ear till now, I wouldn't know as I never followed up. I think it was
https://dvcreservations.com and their FAQ states among the things they do, "We check dates and make reservations for you" which they can only do with login access.
So far, my experience hasn't been negative, my other renters have all paid in full or a deposit and remain in contact.