Giving regtest, simnet and any other #bitcoin
test-"net" a distinct IDs of any sort is a bad idea. It just increases work for developer integrating Bitcoin. And the end user doesn't care - test money is test money, no matter on which fake network.
Because of bech32 addresses using a different address prefix on regtest vs testnet, you can't just take a piece of code and run it against a regtest-simulated test cases, without explicitly taking care of regtest prefix, which isn't even mentioned on https://en.bitcoin.it/wiki/List_of_address_prefixes …