I enter "init 5", I expect the graphical system (usually X11 with a chooser) to start.
Different UNIX/Linux init subsystems handle this differently, but the 1/2/3/5 runlevels can generally be counted on to be the same.
Breaking this is introducing incompatibilities for the sake of being different.
Why? If you have to edit inittab, it shows you the meaning of each runlevel just above the "Default runlevel" line as the (grand)parent post shows. Not exactly "breaking things to introduce incompatibilities".