@Myell0
Yep, it's happened to me too. You are trying to be accommodating and help the guest out, but it backfires.
I used to let guests drop off their luggage early, making it clear that they needed to come back later for the actual check in. The guests would happily agree to this in writing, but some of them then take advantage of the situation, e.g. arrive in the morning and demand access to the room, bathrooms etc. and the key, even though I was still in the middle of cleaning and turning over the place. They would leave me low ratings on cleanliness if I said yes and low cleanings on check in if I said no (likewise with guests who just show up early and are denied access). When this happened with two sets of guests on the same day, I had had enough.
Now I never let guests come early (unless I know the cleaning will already be done, i.e. I have a gap between bookings) and make it very clear on my listing that they will not be granted access if they just show up. It seems to work.
I don't know exactly what this review says, but yes, I'd agree that you have little chance of getting Airbnb to remove it and a short, factual and unemotional response is the best way forward.