12 /12 for flower cannibus need 12 uninterrupted dark cycle to induce flower I belive... if it would work I would like to go 6 on 6off 6 on 6 off but I bett you would end up with a bunch of herms lol
So you are actually still on a 18/6 schedule just segmented into 6/2 blocks. Even though a straight 24 on schedule will work, plants do generally need a dark period as most growth happens during lights off.