There's a ton of legacy code and email software that will make that not work.

At best, it would be pepsi@pepsi. (note trailing dot).

My buddy used to be root@ws. but only a few MUAs and MTAs could handle delivering mail there, and always with the trailing dot.

You have to put the dot at the end to make it a fully-qualified name otherwise the resolver will think it is a hostname and add the local domain.