The first WLW did see Kelmomas when he appeared. Remember, in the room both Kellhus and the WLW turned to him in surprise.
There's no distinction between that WLW and the Sorweel-WLW. As you said, they are essentially exactly the same. I think the WLW posses the ability to see Kelmomas, he just doesn't because his attention is elsewhere. I haven't read that scene in a while so I don't remember the exact circumstance.
The only issue with this idea is, wouldn't you know it, something Bakker said out of the text lol. Bakker spoke at ZDC, and I believe online, that he was having issues with his eyes, and he had developed a permanent blindspot. I've actually had this same experience a number of times, and its something else entirely to simply missing something that's in the room. Why I bring it up is because he said he started calling the blind spot "His little Kelmomas", which really really implies a much deeper blindness to Kelmomas in the books than a mere inattention. I'm not sure how to square this information with what we actually see in the book.