What is the exact difference between 'tty' and a 'console'?
The console is your physical computer and the various tty are virtual terminals.  

Each tab or window of a terminal emulator like iTerm2.app or Terminal.app will connect to a different tty.  MacOS works the same as this quote from one of the answers on your linked question:


  So when you look to a "text window" on your linux system (under X11) you are looking to: a terminal emulator, connected to a virtual terminal, identified by a tty file, inside which runs a shell.


It is more clear what is happening if you run who with who -a (to show all details) and if you also use the tty command (which returns the current terminal).



An example

Here I rebooted at 13:20, left it on the FileVault password entry screen until 13:25 then opened a Terminal.app session at 13:29.

Last login: Fri Dec  6 13:25:54 on console
A1398% tty
/dev/ttys000
A1398% 


You can see the last logon was 13:25:54 on console (when FileVault unlocked startup disk) and Terminal.app is running on /dev/ttys000.   

Next at 13:30 opened a iTerm2.app session:

Last login: Fri Dec  6 13:29:06 on ttys000
A1398% tty
/dev/ttys001
A1398% who -a
reboot   ~        Dec  6 13:25   .           1
hali     console  Dec  6 13:25 00:04        97
hali     ttys000  Dec  6 13:29 00:01       577
hali     ttys001  Dec  6 13:30   .         600
   .       run-level 3
A1398% 


You can see the last logon is shown to be 13:29:06 on ttys000 (when Terminal.app was opened) and iTerm2.app connected at 13:30 to /dev/ttys001.  

who -a shows 


console connecting at 13:25 (when password was entered and FileVault unlocked startup disk).
ttys000 connecting at 13:29 (when Terminal.app was opened).
ttys001 connecting at 13:30 (when this session of iTerm2 was opened).


If you boot into single user mode and type tty you will see the result /dev/console (who is not available)