documentation-outside option `valign=c`?

[Explorer-cc]

I was using the adjustbox of v1.3c – 2025/02/26 with TL2025

And I found that in the documentation, about valign:

Here only provide six options' key(without c)

And In the following original code, it defines \def\adjbox@valign@c, and some of the code on Internet remains to use valign=c, which is NOT documented.

adjustbox/adjustbox.sty

Lines 1935 to 1939 in 775d550

	\def\adjbox@valign@c#1{%
	\leavevmode
	\hbox{%
	$\vcenter{\hbox{#1}}\m@th$%
	}%

Is that should be complemented? Thanks!