I have read a lot of places that aero crankset gives a very little aero benefit, if any at all. On one of the Marginal Gains podcast, with Josh Poertner (owner of Silca and former chief designer in Zipp) said that aero cranks do work.
Yes there are marginal gains. I can’t speak to the exact data, but there was someone testing frames and they couldn’t figure out how they kept losing to another frame. The only difference was an aero crank on one. They had some spare 3m foil tape lying around they made a quick make shit aero crank and the data improved. TJ and I have been making our own aero cranks for many years. Turns out it works pretty well to as a disc wheel valve hole cover. I have heard of some other data as well that was positive for aero cranks from Trek although admittingly it was very close to noise but if you talk to Carl I believe he would say there was something there.
I think I’d rather have a solid chainring body like that especially if it hid my power meter from the wind. It does weigh more and that’s a metric people definitely look at when purchasing cycling equipment.