Actually, what you linked states different amounts depending on application type and/or other conditions:

The Store Fee is:

i. Thirty percent (30%) of Net Receipts for: (a) all Apps and In-App Products made available in the Store and billed to Customers on a non-subscription basis, and (b) all Games (and In-App Products in Games).

ii. Fifteen percent (15%) of Net Receipts for any Apps that are not Games (and any In-App Products in such Apps) that are billed to Customers on a subscription basis.

See also this blog post:

https://blogs.windows.com/buildingapps/2018/05/07/a-new-micr...

The thing is, nobody really uses, or has to use, the Windows Store. Which is decidedly not the case for iOS.

The better comparison on PC is Steam, which takes basically the same cut as Apple takes.