I'm glad you share this, I've seen similar reports online (no major issues from not rinsing!). I love calling BS on myths in this hobby.I am not saying it's right or wrong but I have never rinsed/washed BDBS. I have always just opened the bag and dumped it in.
Any film on surface of water goes away in hours. Fish have always done fine.
For me no issues at all (yes small sample size!).
I would be curious to see if anyone out there has had issues/problems that were related to not rinsing it??
The only issue I've imagined is cloudy or semi-oily water. Much of which I could imagine being a non-issue with initial water changes and cycling.
I would only suggest rinsing well to help keep water clear on startup, but if it's not necessary that's even better.