Anyone use these on tap installs ?

Out of interest why would that not be by the book? Is it because they are not full bore? If so surely they are so close to the tap itself where there is a much bigger restriction?

P.S. I like the name. Just need to insert a "k" into the word and they'd be the nuts !

A normal ISO has tapered seats designed to compress an olive, the edge isn't flat.
Tap tails with the rubber washer in them are designed to sit against a flat edge, like on a 1/2'' union or the tap tail adapters Woodbine linked to.
The sharp edge of the ISO will cut into the rubber washer of the flexi which could stop it from sealing, although I've done it for years and never had an issue I suppose if someone gorilla'd it up it might cut through the washer.
I'd like to bet it's a 'get out of paying' tactic for insurers though. 

The end of the threaded section is not ground flat on an iso so can cut into/through the rubber washer on the flexi if you tighten it too much. I usually just connect onto the iso though unless I'm making a special effort. Never had a problem.

I wouldn't pay that for them, tooooooooooo many ££££££££££££££££'s   a standard iso is about 75p

my sentiments exactly PB,I've used iso's for yonks and never had problems,