WCB and FormT90

I am  status indian receiving interest income which is tax exempt if earned on native land.  I check the box on T1 Pg1 at Tax Exempt- Indian Act.  I complete the T5's  for the amounts and also enter that aggregate amount on Form T90 to offset the income

I receive a survivor pension from deceased husband. I enter that via T5007 and it automatically got inserted on the T90 IF you have checked the Page1 tax exempt query noted above.   I know WCB payments are non-taxable and deducted at Line25000 when a person does not also use Form T90.  Form T90 is for income exempt under the Indian Act . TurboTax is using a shortcut and incorrectly so.  To confirm, I unchecked the Tax Exempt- Indian Act box on T1 General Page1 . Sure enough  - WCB then appeared on the lines 14400 and 25000. 

Question:   Shouldn't WCB  impact Line 23400 via the entry at 14400  so it is included within the threshold amounts for the clawback calculations??  Is there ever a situation that a payment from WCB is  taxable???