I lately discovered this too and wondered where the problem was. This explains it. I can follow your argument that Google also allows SSLv3. Nevertheless I applied the recommended settings from cipherlist as an experiment a week ago (see here https://ssl-tools.net/mailservers/box.letterninja.me). Didn’t had any problems yet.
The implications for SMTP are completely different than for the web (HTTPS). I don’t think dropping SSLv3 here makes email any more secure at all, but it could prevent a legacy email server from emailing you or force the legacy server to downgrade to clear text (as bad as SSLv3 is, it’s probably better than clear text).
I don’t want the box to prevent people from getting legitimate mail for no real reason, which is why the SMTP port 25 settings are conservative.