I am sure there are many other hosts like me who have experienced issues with getting guests to agree to an arrival time within the check in window. I have lost count of how many times guests have asked me to check in much earlier, and some times much later, even though my window is 3pm-9pm, so pretty standard for an Airbnb. I've had to make a real point of it in my house rules.
So, it really infuriates me that Airbnb is now asking guests if the host was flexible about check in as part of the review process. This is going to give guests the impression that the host SHOULD have been more flexible or offered to let them check in at any time (regardless of whether the previous guests had checked out or not or the time it takes to clean and turnover the listing - a lot of guests simply never consider these points) and may well impact the star rating they leave not only for check in, but overall. It might also encourage them to harass the next host about check in time because they will now think it's something they are entitled to.
Airbnb needs to remove this from the review process ASAP.