Apple should be trying to empower users with safe abstractions, not lock them down even more.
“Imagine what your computer could do if it was an iPad Pro”.
And in fact, I can currently choose the experience I want if I decide I want a typical multitasking desktop—by putting down the iPad and going over to a Mac (or Linux, or Windows, or FreeBSD machine, or whatever). Or, to extend the "I like a tablet that becomes things, modally" way of thinking about it, by putting the iPad in Remote Desktop mode and connecting over VNC or SSH or RDP to a traditional desktop or server.
I do agree that this is an issue, but I wonder how much of one. I feel like there is quite a bit of inertia behind iOS style "apps" right now that a sizable mass userbase will not use your service if it is a desktop-style interface, because that sort of interface is unfamiliar to them.
Only for very niche apps would you be able to survive on desktop app alone. Many fo those niche uses would be geared towards power-users who are likely more used to a desktop environment.