I've seen a few people talk about their experience having phallo who didn't need to be on t. You may be able to find them through the search bar. A lot of nonbinary people also get phalloplasty. U/nonbinaryphallo is awesome and has been super kind to share their entire experience. Overall it's definitely possible, and I'd say you could get diagnosed with dysphoria as well. Trans people don't all have the same forms of dysphoria and a lot can get insurance without bottom dysphoria, so I don't see why it wouldn't go the other way around. Or, worst case scenario, it's just insurance, so you don't really have to specify that you aren't binary. Best of luck!