Why not hss?

This does help, thanks.  But it also opens up some more questions which I will research instead of asking all here, with the exception of this: it seems that as the power level drops and as the fov gets wider, the GN drops, as I can see in the specs (attached) of the F43AM.  So then, back to my original question, how is switching into HSS and losing some of that power any different than decreasing the power manually by shooting less than 1/1 or with a wide angle?  I feel like I almost have it, but am getting stuck just shy of wrapping my head around this topic.  Thanks again for the help.

P.S. if I'm reading this right, it also looks like switching into HSS at 1/250 increases the GN by a factor of about 4 over the SSS at 1/125.  Interesting.

P.P.S. it looks like the GN doesn't change at all between APS-C and 35mm format.  Also interesting.  Not sure I get that.