It's a bit disingenuous to expect Twitter or any other social media to actually delete deleted data, except perhaps through a GDPR request or similar. Plus, if your account gets hacked and deleted, or if you delete the account and rejoin, you might be very happy that they didn't actually delete anything and are able to restore your account. (I'm not a fan of social networks or what they do with our data, but the database administrator in me tends to side with them on that front. Keeping data around is a lesser evil than losing it.)