The lawyer likely advised not talking about it more publicly.
Almost any lawyer won't present the world as black and white, but rather in quantities of risk - and even saying "we've taken the project down and it wont be coming back" is a risk if that attracts attention to your past distribution of the software and causes others to mirror it from archives.
Would it make sense to make some disclosure of "it's not coming back and no PRs adding similar functionality will be entertained for this reason?"
Additionally, it seemed like this page[1] (discussed previously[2]) details some reasons why some publicly visible source code projects should be able to include code that implements things otherwise under export control.
Almost any lawyer won't present the world as black and white, but rather in quantities of risk - and even saying "we've taken the project down and it wont be coming back" is a risk if that attracts attention to your past distribution of the software and causes others to mirror it from archives.