Another question is as follows:

I saw special (ie not normal) routing fares where HIP is applied. At the same time I saw fares where text rule says "No exceptions to HIP/MPM", however, in fact HIP check is not applied. These were specific airline fares (ie not IATA fares).

Can anyone advise on what is the rule here?

PS: I also read fares where the text rule and the autopricing went different ways in respect of Max stay. Can this example answer the original question - oe the reason is that text validated for autopricing if in fact not always that valid?