Yes apologies for the confusion. Max HD tends to be for customers without the line speed to get 4K/Ultimate to their TV box, but we don't want to deny them Ultimate on our apps - so they can access it through those platforms.
And yes EE 5G customers and EE with an appropriate bolt-on can also get. I was speaking more to our BT TV base but sorry that was unclear.
In any case - the OP can't get Ultimate because they're on an app-only package.
Thanks for helping to clear that up @scointer !