[mst]

AF point coverage of a D850 / D5 are exactly the same in APS-C mode as with a genuine APS-C D500. All three bodies share the same AF module.

Yes, I'm aware of that. This was also already true with the D300 and the D3 series cameras (at least in terms of coverage). However, I always felt more comfortable using the D300 viewfinder with the wider viewfinder (!) AF coverage than any of the D3-series cameras when I already knew I'd have to crop later (due to lack of focal length, for example).