You can reassign real device to any of these names

Reassign and actually use all of them are different things.

MSDOS 3.3 had COM1, COM2, COM3, COM4, LPT1, LPT2, and LPT3. LPT4-9 and COM5-9 was not part of MSDOS.

IIRC those were mapped to specific I/O and IRQ Ports back in the day.

  COM1: I/O port 0x3F8, IRQ 4
  COM2: I/O port 0x2F8, IRQ 3
  COM3: I/O port 0x3E8, IRQ 4
  COM4: I/O port 0x2E8, IRQ 3

I also remember, there was a while where there was no IRQ sharing. So some machines couldn't use all the COM ports available. Or you'd add in like a modem, and would have to disable the onboard COM port if it was using the same IRQ.

If you do embedded stuff you can easily get above COM100 if you're doing something like testing (if a USB to serial converter has a serial number, it gets a unique COM port). Although I don't think these high numbers have any effect on the file system, just the legacy low numbered ones DOS could have.

Back in the day many of my clients had Windows NT/2000 machines running RAS or RRAS with multi-port serial cards connected to modems for employee remote access. Usually these would be 8 or 16 serial ports per card with multiple cards installed per server.