Discourse normalizes the case of email addresses, both the domain and the username parts of the email are set to lowercase. If your SSO provider site allows for upper case letters in emails, a user could end up with uppercase letters in their SSO provider email address, and a lowercase email address on Discourse.
I am not aware of any other email normalization that is done by Discourse.
This will work if the require_activation parameter is not set to true in the SSO payload.