Identifying iOS users as a target for Apple's monopoly is no more circular than identifying Google-branded (ie. Nexus et al) Android users as a target for a Google monopoly. Non-Google branded Android can, and often does use non-Google apps and stores so that segment can not be considered to be monopolised by Google. In practice the same is true for Google-branded Android devices as it is possible - and not all that hard - to swap Google apps for others.

As to whether I think anyone should investigate Apple and Google I'd say 'no', but that is not what this is about. I don't think Google should be investigated for the stated reasons, but if the EU insists on investigating something I claim there is at least as much ground to investigate Apple as there is to do so to Google.

Where I live - Sweden - Apple does have a large presence in schools. The situation with regard to IT in Swedish schools seems to be that there is money, but no plan. This makes it possible for 'driven' people to steer their local community in the direction they deem to be the preferable. Many of these 'driven' people have a marked preference for Apple products.