MMS- Are some unreliable with high RH?

[Rubensgt40]

Hi all. Apologies if this has been covered elsewhere-

We recently consulted on a timber flooring installation moisture-related failure, where a vapour barrier was applied.

The manufacturer subsequently changed their spec sheets to stipulate that, if the moisture content was above a certain level (yes, I said content, not RH- the standards here still make it optional to use either criteria), two coats of their barrier are required instead of the previously stipulated one.

This was an admission of non-performance by the manufacturer and, to their credit, they copped a six-figure sum in remedial expense.

Is there a point where some MMS's will not guarantee performance where the RH is too high? Even if they wouldn't admit to it, do some installers here use a sort of "best-practice discretion"?