If CPP-D is approved - CPP contributions re-reimbursement

Consider this scenario, you were on STDI 3 months then on LTDI and 6 months later had to apply for CPP-D benefits which gets approved say after 3 months (I wish!) LTDI get 6 months of payments from CPP-D because you authorised it, claim is back dated to the day you stopped working which is 12 months ago. STDI payments had CPP contributions deducted, LTDI payments had CPP contributions deducted. Do you get a refund for the CPP contributions that were deducted while you were on STDI and LTDI when you file your taxes?

#1. I’m not sure CPP or EI should be deducted from STD.

#2. I think the amount you get for CPP-D is calculated by you contributions to CPP.
Maybe only up to the last year or the day you stopped working.

I don’t know except I really question #1.

I can understand why they keep on deducting CPP-D when you are on STD/LTDI because not everyone’s condition incapacitates them to the point where it makes them eligible for CPP-D but once you have been approved by CPP-D then there should be some way of getting a refund for the CPP contributions and EI premiums going back to the month you were disabled/the date of onset. Unless there is an argument that by keep on paying the CPP contributions, while your case is being decided, you are in a better position as you will receive substantially more upon approval.