Man, when i first applied for a whitelist I got denied, too and I was super pissed about. I wrote a /very/ long essay about how I felt mistreated and in hindsight I feel like an absolute idiot about it. Shout out to my homie @CakeIsOssim.
What you have to try to understand is, that the requirements or let's say the expectations for whitelist apps is relatively high because the people in charge put the faith in you that you dont fuck it up, to put it bluntly. A HRP environment just has certain expectations of you. Because if you do, they get blamed, too, not just you. So they naturally want to avoid that. I agree, that @niennab has a strict ruling (personal opinion here) but that's nothing bad. She gives constructive criticism and really cares about the apps that are posted. Dont be angry about it, see it as a challenge and maybe ask her in DMs or on Discord on how to improve and what is important to her. I would be surprised if she wouldn't give you more input in private.
Tl;dr I know it can feel "unfair" that your app gets denied but the people in charge have nothing malicious in mind when they do, quite the contrary