That wasn't to be taken seriously.

It's just that the way you put it sounds something like Apple Markting Department would say.
In fact it's more like: Hey! Apple Music works perfectly on your Apple devices. (If it didn't Apple would have failed completely).
So does Spotify. However, to make you pay for AM iso Spotify, we locked everyone else out from the HomePod.
Seeing an ecosystem from the inside should hopefully always result in an excellent user experience, while seeing it from the outside will reveal a more complete picture. And Apple doesn't do well on cross-plattform.
People who lack the outside vision will one day wake up and realize how they locked them self in with Apple.
Since the Apple Music App has been crippled in the past iOS releases (a usability nightmare that made me purchase Cesium music player) it's not even a pleasure to use anymore,... also playlists, history,... will stick with Apple. Limiting your music to Apple devices (and a bad Windows/Android experience) is like buying a supposedly universal aftermarket navigation system like TomTom that will only fully work inside a specific brand of car.
For the same reason I would always recommend using Alexa over Apple. Apple will lock you in with HomeKit, while Amazon is using an open standard (ZigBee). So you can ditch Alexa anytime and use any other device that supports ZigBee (the HomePod does not).
So, take a look outside the Apple ecoystem, and see if AM is really the best deal. Especially when it comes to retrofitting old equipment, something with a Spotify receiver will outperform AirPlay in usability. That costs ~30€ (~40$) per unit, e.g. AudioCast.