You haven't established anything. You and shmerl have come up with filesystems that have even less support than ExFAT, that aren't even suitable for solid state devices to maintain your dogmatic nonsense.
By 'support' I meant in every sense of the word, official and not.
Jolla can not claim SDxc support in any way if they do not support ExFAT.
How are Jolla going to advertise that you can use SDxc cards but not officially and not wth the filesystem that SDxc cards mandate for interoperability?