No, you are correct.
People love to make the assumption that because the earthen were not flesh, and the curse of flesh made them flesh, that the curse of flesh only works on "non flesh" beings.
There are 3 (4 if you count Kvaldir) types of "Vyrkul" that we know of.
- Normal "Big Mean, Fleshy and Blue" Vyrkul. Lets call these "pure" Vyrkul. These were the original "Land bound" titan Vyrkul creations, quite possibly the Vyrkul were actually intended as the original Titan "colony" race for the land portions of Azeroth. Remember, the earthen were originally created to be more like maintenance workers then colonists.
- Cursed "Smaller, Still Fleshy, and Pink" descendants of Vyrkul. Lets call these "Humans" These were the result of the Curse of Flesh working to "weaken" and already Flesh Based Race.
- Iron "Big, Mean, Iron looking" Vyrkul. These were created entirely by Lokien after he got his hands on the Forge of Wills. They are not decended, evolved, cursed or in any other way related to the Pure Vyrkul.
As for the Kvaldir, there is a possible theory that the Kvaldir may have been the original Titan Constructs indended to "colonize" the ocean portions of azeroth, and when the Shattering Happened and dumped Ashzara into their midst, their entire civilization ended up in a giant war, which the lore Flashbacks from Vash'jir seems to indicate they were losing badly. This may be why we never really saw much of the Kvaldir untill recently.