Here's a room - it's 11 ft x 15 ft, has a proper closet, has sliding glass doors that lead out to a balcony, has all full height walls, has a door that closes properly and shuts off the room for privacy; it isn't a walkthrough so you have to walk through this room to get to another room. It's part of the house - you don't have to go outside or through the garage or through any un-air conditioned space to get here. Is it a bedroom?
We have another listing with an 11 x 16 room, with double windows instead of a sliding door, but otherwise meeting the same conditions as this one. Is it a bedroom?
No, we don't think so. Why? We'd rather underpromise and overdeliver.
It seems the problem for both of these rooms is access to a bathroom. The one pictured is upstairs, separated by a catwalk (and the stairway) from the master bedroom - but the only upstairs bath is in the master bedroom. Downstairs there's a powder room or half bath, and one that is between the bottom two bedrooms, what we call a Jack and Jill bath. For the other listing, the "bedroom" is also upstairs with the master bedroom, and the master bath is shared by both bedrooms.
We'd rather call these 3 bedroom homes, with an office, or possible guest room. We can't assume the buyer will be looking at a 4 bedroom home with the intention of making one an office, or planning to use the 4th bedroom for an infant or small child. Rather than disappoint all the buyers who really need 4 bedrooms, and who will object to the bathroom situations, we'd rather market it as a 3 bedroom with options - and have the prospects pleasantly surprised.
Underpromise - overdeliver. Exceed people's expectations.

Agreed. I often see homes listed when the 4th is a "cell" in the basement with no window. Or a loft accessible only through the master. No one is really fooled when they see these homes and it is such a waster of everyone's time.
If the price is right, there'll be a buyer for any home.