Whatever Serif's intentions, the suite clearly occupies a middle ground. For many users it will be professional enough, and the fact it is a well integrated suite will serve the majority of users well. On this thread we are bemoaning the lack of a feature that many of us argue is a crucial part of what we need to be able to achieve with ease. We think it fundamental, but we may just be bellyaching about a process that is less crucial than we think. Personally, I really like Affinity, will never be tempted back to subscribing to Adobe, and if I ever really do need to achieve a true vector free transform I will probably (virtually) dust-off my old copy of Illustrator CS2, assuming it has this feature!
Meanwhile, being able to open the document in Affinity Photo ('Edit in Photo' in the Affinity Designer File menu) does the job in most of the situations I encounter using the Distort filter in Photo. I know it doesn't create a vector transform, and drops to mere pixels, but as I work well above the pixel dimensions I export to, this hasn't been an issue for my exported files. It is a disagreeable clunky workaround, way too clunky, but until Serif decide that they are moving out of the middle ground I guess it will have to do. If they do move out of the middle ground, I hope they don't change their pricing model, which is what tends to happen when things go 'Pro'. Instead I hope they really do subvert and pull-out the rug from under Adobe.