Can I not sync AAC audio files (voice memo's) to my iPhone?

Specifically speaking, I'm trying to sync voice memo files back to my iPhone as music.

They were originally created and saved from various iPhones I've owed over the years.

I allow iTunes (Music app) to sync voice memos from my phone. I name them, categorize them and everything. When syncing the iPhone, I manually manage content. I have all the right things checked for syncing and such.

I think the problem is because they are AAC files. It seems the AAC files won't sync back over to the phone's music app from itunes. I even change the genre from "voice memo" to a custom genre in case it treats those differently. I'm not sure of this because some few random AAC files do transfer to the phone. I have about 600 I'm trying to move to the phone, so I'd hate to have to convert so many files.

I think if I convert them to mp3/mpeg, they might transfer. Is this true?

I just don't like how it converts the original AAC's bit rate to a much lower quality when I convert them using iTunes.

I should note: I'm using an iPhone 12 Pro Max and a Mac Pro running High Sierra 10.13.6 / iTunes 12.6