I had that issue with my former family doctor as well. She read the paperwork and told me, " I can't answer these questions without jeopardizing my reputation and my license to practice medicine in this country." She had immigrated from South Africa to Canada several years before becoming my doctor when her predecessor my first family doctor here when I moved back, had a baby and decided she didn't want to be a doctor anymore and quit.
The questions for CPP disability and the CRA disability tax credit are different. Also, the CRA does NOT consider a chiropractor as being a "specialist" where CPP did, therefore, the report CPP had from my chiropractor, that was also sent to the CRA, was totally ignored by the CRA despite the fact that it was MUCH more thorough in it's explanation of what the underlying conditions are and how they impact my day to day life. My then family doctor disagreed with the chiropractor and voiced that in her report to the CRA even though she herself had done NO xrays of any kind, where the chiro HAD done so.
There were several questions that she said she couldn't or wouldn't answer in my favor to get the CRA tax credit, including, "Is your patient's condition considered severe and long term" per their definitions given in the paperwork. I looked at her and reminded her that I could NOT work in my chosen profession any longer, and although at that time I was looking for work after graduating college (which I went back to school to give myself a chance) was uncertain as to whether or not I'd be able to find employment at all because of the conditions that ail me. She said, NOPE. I reminded her that she herself, to my surprise, agreed with the chiropractor in saying that I would be dealing with the pain caused by the underlying conditions FOR THE REST OF MY LIFE.......and that I had already been dealing with that pain for YEARS by that time, and that I DID have issues walking AND had all kinds of restrictions on my abilities that prior to getting hurt I did not have, ie no lifting ANYTHING over 25lbs, no bending, no twisting, no climbing, no prolonged periods of sitting, no prolonged periods of standing, just to name a few. Her response......NOPE.........and because of her responses which I never did get to read before she sent the paperwork in, the CRA DENIED my application for the CRA disability tax credit, but they did tell me I could apply for it again at a later date, but I had to wait at least a year before I did so. So if you're considering applying for the CRA Disability Tax Credit, make damn sure your doctor is on the same page with you. IF they aren't they can sabotage your eligibility according to the CRA standards. That's what my doctor at the time did to me.
Needless to say, the minute she put HER reputation and ability to practice medicine over MY health and well-being, and did not seem to understand what SEVERE AND LONG TERM meant, that was the minute I fired her ass. Why did she do it? Because she was upset with me for seeing a chiropractor before I saw her when I first got hurt. She's one of the doctor's out there who doesn't believe in chiropractic or other "alternatives" to what she was taught in medical school to be a GP. She wanted to push pills down my throat that I couldn't afford and not deal with the underlying conditions in any way. I reminded her while pain sucks, it also lets us know there's a problem, a problem that simply "masking" it doesn't address. She didn't wanna hear it OR consider what we could do to remedy the underlying conditions (surgery, which as I've said although she wanted nothing to do with it, my current doctor has NEVER taken off the table, but IF they do it, they only wanna do it once. ) So as I said, I FIRED HER ASS and found my current doctor who is willing to work with me, instead of against me. Eventually I'll likely ask her to fill out the CRA paperwork, and possibly the paperwork for a parking permit as well, something else the fired doctor refused to consider.
Had to add some humour at the end. 
