I saw this when it was first shown on the telly a couple of weeks ago.
It looked to me as if Pogo takes his job very seriously and he's very good at it too.
He's a big enough boy to voice his opinion if he wanted a career change.
I also think unless you have known and/or lived with a dog friendly cat it's easy to become alarmed at such a thought and worry about the stress factor, but in truth no one can make a cat do this kind of activity to the frequency Pogo does it unless the cat was anything other than totally relaxed about the procedure.
Almost all rescues that I've come across that deal with both dogs and cats do it and they choose the most laid back and relaxed dogs/cats for the tests because there's no point picking one that doesn't get on with the other species, is there? Defeats the object... Can't comment on the situation you saw, Gill, but I've a lot of time for the rescue too and I'm sure they'd want to know about your discoveries and concerns.