If the purpose of this was to take some of the pressure off examiners, then it has missed the mark
It was nothing to do with Examiners, it was to aid pilots who have difficulty in locating an Examiner in a timely manner (there being more Instructors than Examiners). It is still a 'relaxation' of the rules - even if this new, additional, method of Revalidation does not go as far as you would like.
When I applied for it, I did not interpret "upon completion of the training flight" as meaning "immediately following the completion of the training flight". Had I done so, I would have realised that the "obligation" would be almost useless and I would have saved the £53. My mistake.
The wording is not the best so I am not saying you should have understood it; I agree with Mr Average that it is completely bonkers for the CAA to give someone an additional privilege (or obligation) without some evidence that they understand the privilege and how to apply it.
For those Instructors who will gain it "automatically" upon Issue or Revalidation - they should not unless there is some evidence that this has been discussed (at a Seminar or with an FIE). For those wanting it badly enough that they will pay £53 for the benefit the same should apply.
Guess it is all too late now !