Ah, yes.
The specs actually list a spindle speed between 6000-12000rpm (snapmaker) So it probably won’t turn on at speeds below 6000RPM (or 50%)
In this post someone actually did some measurements on the actual speeds (to validate how correct the numbers are) CNC Spindle Speed - #15 by ODD and it goes between 50 & 100% as well.
The code of the controller and module does truncate the maximum speed to 100%:
( Snapmaker2-Controller/toolhead_cnc.cpp at a0e979a89b301598d8a9c115946928124990eb79 · Snapmaker/Snapmaker2-Controller · GitHub & Snapmaker2-Modules/speed.cpp at 81647d39f56ff0df0ab27869b1fec081412c0b8d · Snapmaker/Snapmaker2-Modules · GitHub)
They don’t explicitly state the lower limit of 50%, so maybe that’s part of the hardware limitation.
24000rpm is out of spec anyway. (and 2400 too if it was a typo)