>Is it same / similar to C-x C-+ / C-x C--?
Yes.
C-<wheel-up> at that spot runs the command mouse-wheel-text-scale
(found in global-map), which is an interactive native-
compiled Lisp
function in ‘mwheel.el’.
It is bound to C-<wheel-down>, C-<wheel-up>, C-<mouse-5> and
C-<mouse-4>.
(mouse-wheel-text-scale EVENT)
Adjust font size of the default face according to EVENT.
See also ‘text-scale-adjust’.
>the need me to zoom in / out
I just prefer it, if I have little text, for it to be big. Why waste it on whitespace?