Why PAT test?

[Paul_C]

Claiming that the blue core (presuming the flex contains a blue core) is neutral implies that it is at 0V to earth which would be misleading when it is in fact at 55V.

I see your point if "neutral" was actually stated - Bad choice of words perhaps to convey what was meant, given that the blue may or may not be connected to an earthed circuit conductor depending upon the supply system in use (and would not be at or near earth potential for most uses in the British Isles).

Just as an aside, how many 110V extensions sold for use on 110V CTE or 3-phase here actually have brown sleeving over the blue conductor anyway?

 

[Spark123]

Just as an aside, how many 110V extensions sold for use on 110V CTE or 3-phase here actually have brown sleeving over the blue conductor anyway?

At a rough estimate, approximately none
Not that I come across much 3 phase 110v systems but if they were using brown, black, grey conductors it is fine but point taken on brown/blue single phase ones.