I take some reviews using the the multithread and "single" test, and the single test is much better that multithreat, I am thinking on that, becouse have more servers saturating a connection must be the best option, but like satellite options using dynamic assignemt like tdma or fdma for upload and is a shared media looks that could be that Starlink protect itself for multitrhead delivery to protect his backbone.
I test in other enviroments using a multiflows froma single source and give better results that using a single one, but I think the winner aproach is as you mention have a warm period, in other solution even delimite the measure time to try to only measure in the peak rate, like out a pause time of 10 second and meause only for 20 seconds.
I will continue doing more test at leats for the next 3 weeks.