Consider the danger he will be in just prior to release. Perhaps Lin's tweets are meant to keep POTUS safe by basically informing the Deep State that he (Lin) has everything Trump has, and if anything happens, multiple other people are primed for release.
This warning is not just a warning from Lin but also a warning that people other than POTUS know EVERYTHING.
The fake news won't be able to push public opinion against POTUS if most of them are locked up.