I think most people who think that way are just thinking it would "work out better". I'm NT and my partner is AS, so obviously I don't have any problem with NT/AS relationships...but if I was a super-bubbly, wanted-to-have-company-every-day type NT, then I could see how someone would be like "If only the AS guy could find an AS partner, then he wouldn't have to get dragged to all these social gatherings all the time" or something like that. If someone is friends or family of someone with AS and has seen them struggle with non-understanding NT relationships, then they might think that someone else who is also AS would be easier for their AS loved one to get along with. I asked my partner one day if he thought AS/AS or AS/NT was a better combo (someone like you or someone whose strengths and weaknesses compliment your own) because even though we have a very happy AS/NT relationship, it still crossed my mind that maybe AS/AS would be easier for him...he answered that it just varies from person to person (which in retrospect was a "duh" and a question I probably shouldn't have even asked), but my point is that even with a wonderful NT/AS relationship, I still wondered if AS/AS would be easier for him, if maybe my NT-ness wasn't a plus for him. So, I know for myself, if I'd ever made a comment about "wish s/he could find someone like him/her" it would've been so that they could have someone who understood them better. I do my best, but I still come at it with an NT mind, so know I'll never understand his mind as well as an AS person would.
Also, I think it's kind of like if you know someone who is a huge Star Wars geek and they live and breath it, then you'd be like "It'd be cool if they could find a spouse who also loves Star Wars so that they could share in their enjoyment of it". If people see it more as a character or personality trait, then they might see it just as a "common ground is good" thing.
I don't think most people who make those comments see anything wrong with NT/AS, but many probably (and at least at times incorrectly) assume that it'd be easier to be AS/AS.
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