"...but rather their bifurcated OS..."
Apple created the different OSes for different use cases that, Apple thought, required different user interfaces. They sustain it for this reason.
"...but are prohibited from doing them because Apple wants to sell you both an iPad and a Macintosh."
No. Apple maintains different user interfaces for different use cases, it is the touch vs. mouse UIs, the large vs. small screens, that drive the differentiation. I'm not even convinced Apple cares to sell you a Mac anymore, or an iPad. Apple sees both product lines as non-growth.
There is nothing wrong with hating Apple's approach, but claiming it exists for bogus reasons is something else. Apple thought Microsoft's approach was wrong, that integrating touch with mouse or touchpad was wrong. It appears they are trying to reverse course on that, but that's the reason iPads are worthless for doing work. Android tablets are also unsuccessful, tablet computers are limited to vertical applications and casual use.
People forget that tablet computers existed a decade before the iPad, it's good for certain things but creation is NOT one of them.