I picked up a flow hive super (national), mainly out of curiosity. If you had to get the whole thing you wouldn't convince me to, primarily on the basis I'd be using langstroth in the brood chamber and at that point cooperating with other beekeepers in the local area (which mainly uses larger sizes) becomes difficult. (Although if you're already buying stupid-expensive things, that would let you use the integrated thematherapy anti-varroa frames from Italy, I guess?)
It's...neat? I mean, that's basically the sum of it. It's nice not to have to faff about with uncapping and extractors and filtering. There's probably even a scenario where you have only one hive (but who does that expects to have bees more than a couple of years?) and it turns out more cost efficient than renting an extractor but that really isn't likely at all. It's not a scam or anything like that, but...it's...
Look, if you want to spend £400 on a situational super with a cool-factor, go for it. Do things that bring you joy. But go into it with eyes open to the disadvantages. Oilseed ****, ivy honey, needing to prime the frames with wax, it being pretty flippin' heavy, etc.