As far as I know, we are the only one of the top leagues still using the manual ‘drawing lines’ system.
You can argue all day about whether the lines are always being drawn in the right place. And we’ve seen from the ‘Mic’d up’ programmes that the choice of which frame to use is almost pot luck, as it seems that one either side is almost offering the exact same image to the naked eye a lot of the time.
But specifically on the point of the tolerance level. Once the computer guy has being instructed which frame to use and where exactly to measure the two lines from, it isn’t a human decision whether the tolerance level is applied. If the two lines that the computer generates were to be overlapping at all, the computer will instead just produce one line alongside an “onside” graphic.