Makes no sense. If Leopold I has a couple of spares from Neuburg brood, he'll likely agree on John being named Prince of Asturias, as unlike Leopold's children from second marriage, his claim to Spain is rock solid.
So, Leopold likely names John Prince of Asturias and even sends him over to Spain as appropriate (I think his Spanish Granny will demand the boy to be in Spain as soon as Carlos II feels threateningly ill, to have a heir to throne on hand and have him properly groomed in Spanish ways), and Joseph gets crowned as the King of Romans (and OTL Charles VI, or his analogue at least, would likely end up earmarked for Church, as was habitual for third sons, and maybe becomes Archbishop-Elector in the future).