I think CASA is correct, ICAO Annex 1 says licence validations cannot be extended beyond the the validity of the supporting licence. So if someone has given you a type rating on a validation, it would not be recognized by ICAO
I don't dispute your comments but the problem is not the validation.
CASA follows a CASR 202.278 which recognises overseas training courses for the purpose of issuing equivalent Australian type ratings. The regulation does not mention recognition of operational ratings.
So my dilemma remains, how do I get accredited by CASA if the training course is not offered in Australia or at least not available to independently employed Australian Pilots?
CASA's answer is to put the rating on a foreign license and then convert it across to an Australian license. I am simply saying a foreign operational rating recognised by CASA should be able to go directly onto an Australian license if the training is unavailable in Australia.