and so-on that went fairly deeply into my CPL knowledge.
But as a CRI you are not required to have CPL knowledge; you had an advantage over the many PPL holders who attempt the rating! You did not of course have to teach a primary exercise: E of C; S & L; or Stalling at the basic level. Yes, the format is basically the same because that is what the requirement is but the depth is quite different. Whilst most FIs will have covered the same base material, the background of CRIs is a real mixed bag, with only 3 hours training it is simply not possible to achieve a consistent standard, some are good, whilst others are very marginal. The transition from CRI to FI has also challenged all those I have encountered.
Class conversion really didn't feature in it to be honest.
I would say that it did:
who had already failed their revalidation by test, and given a list of deficiencies to "sort out" - including stalling, PFLs and circuits
You have been asked to prepare a qualified pilot for their Class Rating Skill Test; thats what the rating is all about.