I don't know you can find that traffic always bunches up. And if one is content to sit in the gaps in between, almost never anybody cuts in. I drove twice 1000 mile trips each way last year and it kind of worked. It's more of a mindset than anything else. Fastlane is not that fast or it would be empty, lol.

The fast lane isn’t always faster is very true! Haha

What I will say is some of this may be the difference between manual driving - and automatic.

If I’m manually driving - where my follow distance fluctuates more due to speed / traffic - almost no one cuts in.

If I am driving where I’m using the vehicle to maintain a perfect set distance, people cut in.

Again, anecdotal