A lot of weight weenies (not all) use a non sram or shimano crankset, 3rd party bottom bracket and eebrakes or similar.
I recently built my SL6 with eTap but after sourcing the only missing part of my 9150 group (shifters for rim brake) I decided to swap back to shimano. I didn't care about the weight difference as I thought it would add just a few grams but I actually ended up losing 20 grams on the setup.
For those of us who utilize only the below parts of a groupset, here's how it worked out:

I was pleasantly surprised. It really shouldn't change your mind if you love eTap (i love both groups for different reasons) but thought I'd throw it out there for people too lazy for the math like I was
