No … they mean drop to the TTY - an allusion to the old teletype terminals, though we dont use tape and such any more … In windoze terms it would be like ‘dropping to DOS’ …
Hitting Ctrl+Alt+Fx (x being a number so … F5) would switch terminal sessions … by default one, often F1 or F2, is graphical and the others are ‘bare’ …
The point of doing the upgrade in such an environment would be to avoid any (apparent?) system halts due to some sort of graphics break during more strenuous upgrades to drivers, X, DE, etc.
(note - what is often referred to as a terminal on your desktop, such as ‘konsole’, is actually a ‘terminal emulator’ … theres some fun history there if you care to dive)
For some incidentally related information maybe see this:
[HowTo] Resolve an unbootable Manjaro (black screen, login failed, cant boot, etc)