I'm pretty sure the reason "verification code" is blocked is because people will buy a bunch of retail prepaid unlimited plan sim cards and use them to send A2P

I'm pretty sure the reason "verification code" is blocked is because people will buy a bunch of retail prepaid unlimited plan sim cards and use them to send A2P messages like verification codes instead of paying Twilio or someone like that. Carriers don't like this because they charge more for A2P SMS than P2P.