Didn't say they didn't fit I said they aren't 100% right as it's either the ball joint angle or the length (can't remember which) is slightly different, fitted a set to a S1 before and didn't drive as nicely, same as fitting non powersteering arms to power assisted Fiestas, and fitting the arms that are sold on Ebay for FRST that arn't designed for FRST they are just std Mk3 arms which are listed by some companies for the FRST but FRST/XR2i/RS1800 have different arms than the rest of the Fiesta range.
There's a reason parts are listed differently and just because they fit doesn't mean they are 100% right unfortunatly sometimes the wrong parts have to do but when you can get the right bits why not use the right bits.