I don’t think the qualifier was necessary. I think it was used to describe the obvious nature of anyone owning the sole software distribution means on their platform, it gives them a de facto monopoly on that means as opposed to a natural? monopoly where they just got so big they fell into it.

Apple unquestionably monopolizes the App Store. Whether or not you consider it a substantial monopoly is it's own thing, but the App Store itself is segregated from competition.

This word is not used in the real world anyway. And depending on the jurisdiction, there often isn't even a minimum 50% market share to qualify.