Why do you insist on posting poor and confusing advice regarding mist-coating, joe? Is it because you like the attention? Maybe you like to cause people problems? Or, is it because you just don't know what you are talking about?
Using diluted contract matt for mist coats is the method that the pros use and it has proven results and longevity. Your methods of recommending vinyl emulsions for mist coats (although perfectly acceptable when done correctly) and even the use of PVA combined with emulsions is the way that DIYer's do things after reading poor advice. They then come to this forum for advice when they have issues when such methods have been used.
If you are suggesting that contract matt cannot be diluted and/or is not suitable for use on new bare plaster, then I suggest
you read the back of the tins and follow the manufacturer's advice.
Honestly, you just make yourself look sillier and sillier every time you criticise correct methods and try to justify your problem-causing ones.
And, before you try to justify your arguments, you
can paint over contract matt with vinyl emulsions without any issues, and it
does satisfy the porosity of the plaster to allow you to do so.