Instructions for Form 8829 from IRS say that mortgage insurance premiums for those not itemizing deductions will also go to Line 16 excess mortgage interest. In TT, do not use the mortgage premium screed to enter this number, but instead, add it to the interest you are reporting as excess mortgage interest.
I agree with you that this matter is not well explained. This problem should flag once the final decision is made whether to itemize or take the standard deduction.
Hope this helps
