From Holdo’s perspective, there’s no guarantee whatsoever that Poe will lie over like a lap dog and accept her plan. I don’t know why you think she should be able to assume this just because we as an audience see he does later, but that she shouldn’t have confidence that she can take back control. It makes a whole lot more sense to me that she’d trust her and her compatriots’ skills more than she’d trust Poe’s judgment, especially considering the whole reason she hasn’t told Poe in the first place is she doesn’t trust his judgment. She’s completely consistent here, staying steadfast to her plan and her judgment of Poe all the way (like I said, Poe attempting mutiny only serves to make her trust him less).
Not to mention, we can’t even really know for sure that Poe would’ve taken it well. There’s an argument to be made that having Leia tell the plan to him after his plan and mutiny was dead and buried and this was the only option left made him more open to Holdo’s plan. Who knows if in the moment, while Poe was trying to get everything to work, that he would’ve just given up and rolled over.
But this whole idea of Poe being untrustworthy is so bizarrely contrived. There’s nothing up to this point that indicates he has ill intentions or would not be amenable to Holdo’s plan. Okay, he disobeyed Leia’s order to retreat, but it turned out to be the right call given that the Dreadnaught would have destroyed them all upon re-entry into normal space. Even immediately after his demotion he is given the green light to ‘jump in an X-Wing and blow something up’ which shows that there is significant ambiguity to Leia’s position in this regard.
And why doesn’t he trust Holdo? It can’t be a gender thing because he happily works alongside a whole bunch of very capable women - Leia included! It can’t be Holdo’s appearance given that he also works alongside aliens, droids, and lobsters in flight suits. It’s like this whole “she’s not what I expected” routine from Poe is suddenly pulled out of thin air to force a conflict in order to generate this particular storyline.
And what’s the lesson here? What if a similar situation arises and the next leader who withholds information turns out to be a traitor after all? Will Poe sit idly by because, well, you must never question authority?