The email is missing because we delete user ID from session after sending activation email and that is indeed the correct/safe thing to do.
Considering this is an edge case (and can be reproduced by accessing /u/account-created/resent directly), I updated the code to show generic success message (on reload) as per:
https://github.com/discourse/discourse/commit/1381dc603d4dcad3c2ac6e12488692241fcbc79d