It means booting into runlevel 3, which is not the same as TTY3.
And another example of “AI” being rather dumb.
There is no reason to remove nowatchdog .. unless you want watchdogs. Either way it wont affect how your system boots. Removing quiet is similarly only helpful in the sense that you will see more text while booting. splash of course is the boot splash.
The 3 on its own would have initialized using runlevel 3 (no GFX/GUI).
See a real guide;
This would seem to indicate you performed a partial-upgrade or similar.