Ok, old thread already but still took the time to check things out. Scores will differ from browser to browser, firefox tests very poor while edge seems like a rocket. So I would steer clear from this kind of benches. Use cinebench instead, or other cpu benchmarks. But not webbrowser types.
In answer to your question as for the why, an updated browser will already give better or worse performance in this bench, which will likely be the case since you migrated to a new board and reinstalled windows.
I have a 9900k also.