Whilst Airbnb were indeed forced to amend their policy by the UK CMA (Competition and Markets Authority), on account of guests who had actually turned up at a substandard property not being able to leave feedback to warn others (without jumping through hoops with CX), there was never any stipulation by the CMA that reviews should be permitted up to 24 hours before check-in though, @Anonymous. Airbnb came up with that little gem all by themselves.
Gordon Ashworth, CMA Project Director, said at the time: "We were concerned that, if someone cut short their stay, it was too hard for them to leave a review under Airbnb’s existing reviews system and so we are pleased that Airbnb engaged constructively with us and committed to making the necessary changes"
In fact, technically, Airbnb are potentially in breach of the CMA ruling because..
"The CMA considers that review sites should publish genuine reviews, including negative reviews, provided they are genuine, lawful and relevant. Failure to publish genuine reviews may breach consumer protection legislation, in particular the Consumer Protection from Unfair Trading Regulations 2008 (CPRs)"
It's difficult to imagine how a review that contains feedback on several key factors that a guest couldn't possibly have any first-hand knowledge or experience of (accuracy, cleanliness, location etc) - because they've never actually laid eyes on the place - could be considered genuine, relevant or lawful.
https://www.gov.uk/government/news/cma-welcomes-airbnb-guest-review-changes