@Oliver *******
Like I already explained in my comments to someone else in this post, Booking and Agoda are completely different companies that are even headquartered in different parts of the world (Netherlands and Singapore). They are both owned by the same holding company, Booking Holdings. However, each operate independently, and hotels sign separate contracts and offer/manage their listings and promotions separately on the two sites. However, both sites show lower offers, when applicable, from the other site as "partner" listings in order to provide the lowest possible price, in cases where the combination of promotions and coupons offered on one site would result in a lower price than the other. Hotels can also select whether to allow their listing to be shared on partner sites so it doesn't HAVE to appear on the other. The two site's backends are completely different from each other and don't tie together for the hotelier. So it is perfectly plausible to have a problem with one site and not the other. Booking(com) has made a corporate decision NOT to offer Test & Go/Sandbox testing/AQ packages on their site, and to only indicate when hotels are SHA+. However, the rate shown on Booking is only the room rate. So many are booking it and showing up in Thailand with a non-qualified booking that doesn't include the RT-PCR test and SHA+ transfer as required for Bangkok, Samui, and anywhere other than Phuket. Agoda does directly offer AQ packages (and before it Test & Go) so that's why the government is OK with it.