I've done a little bit of research, and have reached the following conclusion regarding Superman's S logo, which may or may not be accurate.
The
police-badge shaped "shield" S that we see on the cover of
Action Comics #1 was Jerry Siegel's original design for the logo, and was only used in pre-1936-ish drawings.
The yellow triangle design is used inside
Action and we also see it on the cover to
Superman #1 (on which the above forthcoming action figure is based). This was a later redesign.
That's my theory
. Corrections are welcome.