I see two listings for this in the MS App Store. There's the official one that this WinSCP.net website links to (https://www.microsoft.com/store/apps/9p0pq8b65n8x?cid=downloads), listed in the store with Martin Prikryl as the developer name. This is the one I myself purchased years ago.
There's also another one with an identical name, near-identical description, for $4.99, with "Watch App" listed as the developer name. It's located here: microsoft[.]com/store/productId/9NQNX8GPN50M
I'm not sure if this is someone trying to just make money by luring users to buy from them, or potentially a malicious copy of the app, who knows. Just wanted to share it.
I assume the real WinSCP team can report this to Microsoft as a violation and get it pulled if that's the appropriate thing to do.