So you're saying that Google (or any other company for that matter) is better off NEVER EVER releasing services that use potentially open protocols because later on if they would ever consider changing those to a closed protocol it can be seen as anti-competitive. Better to just always use closed protocols.
The best way to counteract that strategy is a more complicated topic.
You are correct that creating bad rules around the removal of open protocols could end up dis-incentivizing usage of open protocols, but that doesn't mean there aren't some good rules that won't (I don't claim to know what they would be).
I think it makes sense that we create anti-trust or consumer protection laws that cover the circumstances under which services with high market-shares can remove support for open protocols.
I even see a potential argument to require services with sufficiently high market-share to implement open protocols.
EDIT -> They did NOT, see below comment by nvrspyx.
Apparently they did, and removed it around Mojave-era or so...? I'm not familiar with Apple products, this statement is based on https://www.reddit.com/r/MacOS/comments/9l5xu7/mojave_now_th...
> Also iOS will always remind you Safari is there, as it is the default browser and that can't be changed.
> When did we have iTunes on windows Phone either?
I agree that incompatibility in general is not on its face evidence of anti-competitive behavior.
> Facebook offered XMPP messenger?
They did, then once they imported users to their platform, turned that feature off. That might have precipitated Google to turn off XMPP federation on GTalk to stop the bleeding.
> Shall Google ... not make changes they think are better(even if they are worse overall)?
Nobody said that Google cannot make any changes to their products. Moving from a standard 'everyone' can use to a closed-off system could be argued as anti-competitive, hence its inclusion on the list.
> Lots of developers didn't develop for Windows phone. Shall those be investigated too?
Those developers could refrain from developing themselves, but they were not in a position to stop competitors from developing their own apps. Google is in a different position.
> Yes yes, MSFT did make a youtube app, but google has full liberty to decide which platforms they want to make apps for
Google said not to develop the app that way, but this way. MS complied. Google still refused to allow the app for no explained/good/political/anti-competitive? reasons. Google was focused on killing Windows Phone, not the iPhone, even as far back as 2006. Eric S in the Verge article in my above comment "... at the time we were very concerned that Microsoft's mobile strategy would be successful."