I see fairly often different expert advisors being made to trade on any pair. They are never made or tested on all currency pairs. Typically there’s just one pair and it’s created and tested on that. But traders still use it on different currencies and see totally different results. I believe it is only sensible to have a EA developed for one currency pair and trade with it on that one particular pair all of the time.
That’s what Forex Brilliance creators think too and they have created a suit of robots that trade on particular major pairs. There’s no bafflement in regards to what to trade it on and whether it should work better on one pair or another. I believe more developers should use this practice. Not just that, when you are trading by hand you need to consider that to be true for your manual system also. It is a mere matter of probability, once you test and tweak a system on one currency pair, it’s sure to perform best on it. Naturally, I do not say that there are no systems that are universal, but it is’s a lot more difficult to make and run such a expert advisor.