Aah, not that long. 
I think the perfect solution would be a change to core to get the inbuilt user fields to also be searchable. It is a bit of an oddity that custom ones have more functionality than the default ones.
Though the new config pages format might work well for their inclusion. Having the ability to show/hide/disable as well as optionally making them searchable, etc would be a nice improvement.
You should be able to pull this info out using the data explorer though? But I’m assuming this is for their user base to use rather than an admin report?