ael........no it isn't pointless, as it would be wrong to assume that any blood detected in the farces was from your piles.
One can have piles AND colonic disease, coexisting.
To answer your question, I think the test is done properly, and I think is worth doing. It won’t pick up everything but will certainly pick up some things worth investigating.
As to whether you do it or not, entirely up to you. I would.
We have that test on the NHS here in Spain too. You have to put the pooh on a little stick which goes in a phial. If it isn't worth doing, why would they spend so much money on everyone ( older than 60 I think) doing it ?
Yes. Mine wasn't cards, but a little stick. I noticed there was a bit of liquid in the vial, so I suspect it is poured into a machine having been thoroughly shaken in the post.