To me it should depend on the rides failed on a case by case basis.

What if someone failed their private and instrument, when they were a sub-100 hour pilot, then later on their CFI initial? Are the failures at the <100 hour level indicative of what kind of pilot they are once they hit 1000+ hours of TT, and have saved their a$$ multiple times while instructing?

I've become even more cynical of checkrides since I started instructing. I have seen students that I was so sure would pass, I would have bet my hard earned cash on them. They even passed their 141 grad-ride with flying colors and then failed the checkride with the DPE over something completely stupid. Then I had a couple students that I was really nervous about signing off, and that barely passed the grad-ride by the skin of their teeth. But then took the checkride with the DPE and not only passed, but the DPE acted like they were super amazing pilots and god's gift to aviation. It is really mind boggling. I only have one hook and its my CFI initial, but after seeing what I have seen as an instructor, the fact that I never failed any of my other rides is probably as almost as dependent on luck as it was on my piloting skill. Checkride passage/failure can be so subjective and even dependent on the whims of that examiner on that particular day at that particular time.

Also, the whole CFI initial thing bothers the hell out of me. (maybe because it is the only blemish on my record) The FAA doesn't view the CFI certs as pilot certificates. Also, there are a good number of people who have gone to the airlines without becoming a CFI, thus not having to take that gamble. The national average is that something like 70-80% of applicants fail their CFI initial. At the local FSDO here, there was one FAA examiner that would fail everyone on their oral once and then their ride once. In addition to handing out two failures to each applicant, he would turn around and 709 the CFI that signed the applicant off. As a result of that, our school started sending CFI applicants to another FSDO, and our POI threatened to pull our 141 status for doing that. Absolutely ridiculous.