@andysendo clearly the people who made the Geany UI have a different usage and workflow than yours.
It was worth them adding the capability of modifying the encoding *inside* Geany and mentioning it in the manual.
@vfaronov indicated the intended way to use Geany to reload an already open file with different encoding, and as that also sets the document encoding it makes no difference in terms of UI actions, just "reload as" instead of "set encoding". Neither is "better", they are just different ways of achieving the same thing.