A good thought, but sadly no. The en_US is definitely %g:%i:%s %a which is correct.
The default in the code (/library/WT/I18N.php) is actually %H:%i:%s but then each language, including en_US has their own translation. For American it translates to %g:%i:%s %a
H = 24-hour format of an hour with leading zeros 00 through 23
G = 24-hour format of an hour without leading zeros 0 through 23
g = 12-hour format of an hour without leading zeros 1 through 12
(the %a at the end adds the “am/pm” suffix)
But all of these are just for display anyway. They don’t change the underlying time calculation.