One of the amenities that MegaMarket offers is a water cooler (music app). Then, one day, they decide to change the water cooler into a house brand coffee machine (music streaming) that has the water tap function stuffed away on its back.
All the other coffee brands are in the back of the store in a rack, all next to eachother. Meanwhile, MegaMarket’s coffee is front and center right as you walk into the store. And a bunch of people who’s store route never took them to the back of the store now also try coffee and get used to buying it each month.
See how that horribly disadvantages the singular coffee brands? And none of them have the capital needed to start their own supermarket. And even if they did, their new grocery platform could never build enough marketshare before MegaMarket coffee entrenches itself in the coffee market.
If Apple said to Verizon, AT&T, or T-Mobile that they could only sell iPhones if they only sold iPhones and _then_ used that position to bundle other services they would look like Microsoft. I could see potentially on the supply side (buying all of TMSCs most cutting edge capacity) Apple has that power, but on the consumer side they have no price control in any market (Apple products are not a market).
It's a strained argument to say that if they hadn't have put the OEM agreements in place that they would've been completely unchecked by the antitrust authorities in the browser market.