It does not get skipped, but rather does not overwrite the existing flwm binary when used with tinycore.
I will rename flwm in base tinycore to flwm_topside since, in fact is a derivative of flwm. That way, even with tinycore, you will be able to use the flwm.tcz extension. This will be in 2.5 final.
It works in microcore as there is no base window manager, therefore no collision.