I am not sure, I just give my two cents.
When you use "Play Sample" the program use the first free channel to play the sample, and so you can ear multiple samples.
When you force the channel every time you click you interrupt the last sample and replay the new one.
This is my idea, someone more expert than me can give a better explanation.
looks like you are right ... So in this case i see only one solution - generate sounds on 3-4 channels one by one.
Thank you !