According to the dictionary [0], the usage is fine. You seem to use the following definition:
> 3 : lacking individuality, distinction, or recognizability
Which is clearly not true for Twitter users due to their handle and public profile. However, it's also defined as:
> 2 : not named or identified
The example is even a book author, which you'd classify as pseudonymous. I think in this case it makes sense to make the distinction, since there are anonymous social networks, but it's not technically wrong.
> 3 : lacking individuality, distinction, or recognizability
Which is clearly not true for Twitter users due to their handle and public profile. However, it's also defined as:
> 2 : not named or identified
The example is even a book author, which you'd classify as pseudonymous. I think in this case it makes sense to make the distinction, since there are anonymous social networks, but it's not technically wrong.
[0] https://www.merriam-webster.com/dictionary/anonymous