I don't know if this applies to a laser
But on a CNC mil or lathel, the machine will wait on the M3 (spindle start CW) until it is up to correct speed, ( this allows the machine to be at correct speed before entering the cut ).
this can be sped up, especially when the head is in the "home" position, and there is a distace to travel before cutting
Check for an "Ignore up-to speed answer back" or similar M-code ( it is a one shot -meaning it only works on that line of code )
mill programming example
The 1st M3 tells the spindle to start, M133 to not wait for the up-to speed check and go do the next block of codeCode:T1 M6 G0 X0. Y0. S5000 M3 M133 G56 Z1. H1 M3 G1 Z-......
The 2nd M3 is to do the full check that it is on and at the correct speed and if OK to continue ( which would only be momentary ).