You've basically made my point for me.
The post I replied to was saying that DS3s weren't compatible out of the box due to "button layout". If that were such a concern or a viable reason, GameCube controllers would face a similar issue, dongle or not, since they lack Home buttons (and now Share buttons with the Switch, which was one of the precise examples listed in the post I replied to), among other major differences. So the fact that it can work with 3rd-party device assistance makes the argument that I replied to about why Sony themselves won't permit it even MORE bullshit.
Maybe look at what was replied to? Because yeah, the fact that using GameCube controllers requires a dongle doesn't invalidate that it has a VASTLY different button layout and still works across 3 consoles it wasn't designed for and doesn't share a point-for-point interface layout with.