I need to know, beyond “I think” or “I was told”, whether or not CIC states a point from which students must start to count their work experience.
No one's stopping you from reading the information provided by CIC. To quote PMM, "when all else fails, read the instructions."
For example, the instruction guide. http://www.cic.gc.ca/english/information/applications/guides/5609ETOC.asp
It says:
Note: Any periods of self-employment, unauthorized work, or periods of employment during which you were engaged in full-time study (e.g. work experience gained on a co-op, off-campus or on-campus work permit) will not be included when calculating the period of qualifying work experience.
There's also the OP 25-A, the instructions to visa officers for CEC applications (post-January 2, 2013):
http://www.cic.gc.ca/english/resources/manuals/op/op25A-eng.pdf
page 7:
For a student who had graduated from a Canadian post-secondary institution, only work
experience gained after graduation will count towards meeting the work experience
requirement (e.g. post-graduate work permit).
My personal opinion is this: as of January 2013, to be eligible for CEC both students and foreign workers must work full-time for a year in a skilled position, and that is. In other words, all your work experience counts as long as you have a valid permit or authorization and your position is level 0, A or B.
Alas, CIC didn't hire you to write the rules.
Students are no longer required to submit graduation documents (CEC checklist), and after graduation Off-campus Work Permit holders are allowed to work full-time.
True.
That is why I consider all experience gained after graduation in a skilled position should count for CEC, even though the respective PGWP has not been issued.
This point has been debated for years, not just since the January changes. Alas, CIC still has not clarified it - the contradictory information remains. You are free to act on your "opinion" but don't be surprised if your VO doesn't share your opinion. The "better to be safe than sorry" advice is still good.