You didn't look into the code, did you?
I didn't use OnGameFrame, I've used a timer that repeads itself in the interval of sm_attackmarker_marker_tick. So if sm_attackmarker_marker_tick is 2.5, the markers are drawn every 2.5 sec.
So this plugin has a tick by itself.
English isn't my native language, so is tick the wrong word for that cvar? I know I've could have used sm_attackmarker_marker_interval, but its longer so I thought tick describes it and is short.