This is a misconception. Macros execute left to right. When you put multiple /powexec commands in one macro or bind, what happens is the client first tries to execute the first power. But then it tries to execute the next power in line, overwriting the previous attempted power execution, and then this continues for every power in the macro. This all happens virtually instantly, before the client or server can actually queue a power. You can only have one power queued at a time, and queueing a new power while another is already queued cancels the prior queue, so what ends up happening is only the power farthest to the right actually gets queued for execution.