I don't know if I completely agree with this statement, only because Orpingtons were developed in the UK and thus I am partial to their Standard, believing it more accurately reflects the bird that the creator envisioned. That being said, English anything are typically larger than their American counterparts, just look at English Budgies or Zebra finches compared to American Zebra finches or parakeets.
Technically, yes, all three varieties would be considered dual-purpose, although the Utility Orpingtons are probably much better egg layers and not as productive when it comes to meat birds.
Show-quality birds that adhere to the APA's SOP would be considered "Heritage" not because they are closer to the original type, but because they aren't "utility" or "production" lines.
I am currently working with Silver-laced, Blue/Black/Splash, Lavender, Chocolate, and Recessive-white. This is my first year with them but I am enjoying them and the challenges they present so far.