You are very correct in assuming the delay valve may be excessively slipping the clutch and these two images may shed some light as to why it is so. One is my oem slave cylinder and, while not the best image, you can see the extremely restricted opening the oil must travel through.
The drop in e90 slave cylinder has no such restriction and engages or disengages it at a much more aggressive rate. You slip it as much or as little as you want.
I believe this is why so many people have issues when rolling from dead stop to first fumbling with inconsistent clutch engagement points, amongst other things.
I have 58k on my stock clutch/flywheel and I did the noted cdv mod since 30k. I will say it is a very useful mod to thoroughly modulate the clutch as per your liking. As the same time, you remove the possibility of extra, unintentional, slipping because you can engage or disengage so much quicker.
Here is the link for the delay valve mod in case you are interested.
https://f30.bimmerpost.com/forums/sh....php?t=1666477