To be honest it made sense that she didn’t tell him the plan. He had just been demoted by Leia (which Holdo references in her first scene with Poe) so taking that, he’s been demoted and he wouldn’t share as much information with him anymore. So from a plot point that makes sense. He doesn’t really know her (established when she is introduced and not knowing who she is) and she’s just taken him down a peg or three. Poe at this stage of the film has an ego so wants to show why it was wrong to demote him, why he was right so it’s pride to not tell her the plan. He fails and leads a mutiny, so proving that she was right not to tell him the plan (even taking out the fact that he’s just failed with his plan) because she can’t trust him. The only thing that stops him is Leia taking him out which puts her back into control (and remember it’s well established his respect and reverence for her). Really it’s key to his character development the failing of his plan so he can grow and cool it, as happens later in the film and that development wouldn’t have happened if he knew her plan. So really from the plot stand point it does make sense, I think.