Plan term < restatement period; restatement needed?

Plan terminated in 2018.

Owner still has assets and continues to file Form 5500.  (Life Insurance...)

Plan still needs to restate, right?

Yes. The IRS would say the plan wasn't really terminated and at least needs to maintain the document.

Agreed, you don't really have a terminated plan.

Correct, plan is not considered terminated and must be restated. See Rev. Rul. 89-87.