Hi Glenn! I just wanted to add a few thoughts:

The diagram in the spec sheet above is a source of confusion... it identifies the track width from wheel face to wheel face, but track width is universally measured from wheel center to wheel center, just like you had done. So the number is correct as confirmed by you: ~1514mm, and the diagram is wrong.

However, the "65mm increased track width" claim is not correct based on this information. Because actual track width is measured from the wheel centers, width of the wheel has no effect on the measurement, so you lose 25mm right there, bringing the increase to only 40mm. If you make the comparison to a standard 6.5" wheel rather than an SVT/ST170, you lose another 13mm, and there you get the number hotdog posted: 27mm increased rear track width. For my own edification, I just went outside and measured my SVT's rear track width, which came out to what hotdog posted: 58.5", with the front slightly wider.

It appears that Ford was altering the term "track width" for marketing purposes (if Ford ever actually made the claim "65mm wider track width") and only refers to the difference in width of the RS from wheel face to opposite wheel face compared to a standard Focus with 6.5" wide wheels, and this is only in the rear. The difference in "actual" track width is indeed only +20mm front/+27mm rear.