Without seeing this bottle in hand, I imagine the little flip top is quite stiff to flip up, so wouldnt be an issue in a bag. You wouldnt think it would be a problem given that it is sold specifically for fuel use.
Flip-tops typically have a little notch for your finger. If that caught on something while putting it in a bag, there would be more than enough force to open it. I’ll stick to screw tops.
Could be just the lingering trauma of said shampoo bottle a long long time ago.
I do have a subconscious habit of checking that screwed on caps are actually screwed on when putting them away