I think the author's main point about concentration is even more important in blitz. My own peak on lichess in blitz is 2117 (super humblebrag) but if you look

I think the author's main point about concentration is even more important in blitz. My own peak on lichess in blitz is 2117 (super humblebrag) but if you look at my rating history it has massive volatility due to playing on mobile phone on bus rides, in bed before going to sleep etc. Concentration != using n-seconds per move... More like not wasting n% of seconds per game with non-game stuff.