This is the dilema since we use lithium batteries. And if it was truth we would be certain of it.

I believe that there is a difference, but I think it is in the range of few percents of capacity lost per year, which means you will be using 60% of the capacity. That's capacity you get after 10+ years of use.

We all know batteries don't last that long anyway.

All that said I do keep laptop on 80% ¯_(ツ)_/¯
since I rarely use it on battery.