You are right to point out the hypocrisy.
There shouldn't be any criticism of the Australia's policy towards RL internationals, similarly we (England) shouldn't be criticised for not playing against tier two teams as it stands. Both countries would embrace an international scene, the issue is the lack of one. There's only so many times we can expect NZ or Aus to play over here.
England knights reserve team playing Ireland, Scotland and co. would generate the same interest that games between Euro teams currently generate, none. However I understand why we would be reluctant to put out a full strength England team to play against them also. Although the beatings would be huge, the main issue is there is no evidence to suggest the profile of the game would be raised any higher. Scotland and Ireland would be made up almost entirely of other Englishmen - or some antipodeans - and wouldn't be given any media interest as is the case with these teams in the RLWC. If you can't generate any interest in Scotland, Ireland, minimal in Wales and France, for a RLWC, then why would a RL six nations do it?
Going back to the main issue which is the lack of an international game, it's not something that is addressed by having teams made up of Englishmen taking on other Englishmen. One reason the game in Australia is much healthier than in England is better decisions are made in Australia. A case in point is the recent talk of an NRL team in Perth. The Aussie RL chief dismissed it as not being financially viable at this point, and instead focused on development of the sport at grass roots level in Perth which in time will make having a professional team there viable, a bottom up strategy. In England it's been a top down strategy. RL teams inserted in places where there is no grass roots for the game to take hold, Paris, London etc. Very costly endeavours. With this proposed RL six nations it's the same top down approach. There's little or no interest in the sport in Scotland and Ireland, very little in France and minimal in Wales. An Aussie strategy over here would be to try to do what they are doing in Perth, establish grass roots first in these places, then think about having a team play games, both club and internationals. The sport in England is run very badly with amateurish decisions made, and, as I said, costly ones.