? It really doesn't.
Yes, a MIDI port (just like a MIDI cable) *always* handles up to 16 channels. That's part of the MIDI specification. If you want to pass multiple sets of 16 MIDI channels to a single device or application, that's why you use multiple ports (for instance, my XV-5080, which can handle 32 MIDI channels, has two (real) MIDI ports on it).
All that's happening there is Kontakt is receiving MIDI from the host - the same old 16 incoming MIDI channels. You can see that Kontakt (as a feature) supports other input ports, but these are "not available" in your screenshot because they are not a thing in this context.
If you run Kontakt in standalone mode, then Kontakt is responsible for MIDI I/O, and it can receive MIDI from multiple devices/ports (up to four, by the looks, which it labels - arbitrarily - as A through D) - so in it's MIDI Settings, you can enable multiple MIDI ports, and so have, for instance, one keyboard playing one loading Kontakt instrument, and a different keyboard, coming in on a different MIDI port, playing another loaded instrument. But it's just a Kontakt label - you're basically using it's MIDI settings to say 'Hey, treat the MIDI port from my audio interface as "A", and the MIDI port from my USB keyboard as "B"', and can just route accordingly inside Kontakt (as you can't otherwise label those A/B/C/D ports as "Audio interface" and "MIDI keyboard" or something more descriptive).
None of that has anything to do with the MIDI specification, it's simply a Kontakt feature of handling multiple MIDI ports in standalone mode. it's also irrelevant in Logic, which handles all the MIDI I/O when Kontakt is running as a plugin (which is why there is no MIDI Settings menu in this context), has a 16 channel bottleneck, and why only the default set of 16 channels (which in this context, Kontakt arbitrarily calls "A") is available, and the multiple port feature is not available.
All instruments in Logic on a track receive one MIDI ports' worth of data, 16 channels.
Logic does have more multi-port MIDI routing options these days though, they finally eliminated the painful MIDI sequencer bottleneck in the environment (but kinda bypassing it) but all the above is still true - it just gives more flexibility in MIDI routing in the main window.