As @smtucker rightly states; I have indeed had this problem on numerous occasions though notably all have been this year. I don't think air has changed the way it's displayed, after all you need to select private room in order to find my listing.
I believe that there's a new breed of guest that really doesn't bother to read listings. As such, I've had three guests this year who claimed they thought they were booking the whole flat.
After it happened a second time I started messaging guests reiterating what was on offer so I have no idea how the third guest was confused about what they were getting.
The worst was a guest who claimed my listing was misleading, gave me 1 star across the board and opened a resolution claim for a full refund. Air did not refund the guest however the guests ridiculous review was allowed to stay. The other guest who didn't read also rated me badly and dinged me on accuracy (amusing given it was all in the listing.) again Air insisted the review should remain.
I have expressed concern to Airbnb about this given these guests are likely to review badly though no fault of my own. Each time Air tell me it's unlikely to happen again but three guests in 4 months is a pretty high occurrence rate.
When the third guest said they didn't understand what they had booked I called Airbnb immediately and they mediated with the guest.
My rate is between £29 and £32 per night. No idea how you can expect a whole flat for that price.
PS two of the three guests who professed to be confused live in this country. So I can't say it's a language barrier.