According to Pythagoras's a²+b²=c² we get 100,00²+1,25² = 100,01² (rounded upwards)
Correct?
Hence running diagonally for the whole home stretch's 100 meters adds a whole effing centimeter to the effort for one line, and approx 8 cm for the diagonal to the most outside lane.
8 cm! That's 1/100 of a second for these guys!
During the home stretch they run with somewhat above 180 steps per minute, that's near 33/100 of a second per step. Let's go a bit generous and say they peak out at 240 steps per minute, that's STILL 25/100 of a second per step.
How much they lose being disturbed (or forced to hold back even a tiny bit) for just one single step probably varies, but surely being surrounded also takes away brain foucs that should go towards forward only.
Going wide on the stretch is something completely different than going wide in a curve. A lot of races would have ended differently if more runners were smart enough to go wide, avoiding the kerfuffle on the inside, totally undisturbed max the whole way.
8 cm extra for going totally free on the diagonal verses what you can lose in all manners of ways in the mix on the inside.