Both of these posters are URM's.. and at least one of them has a very rare major combination. They may not just be sending out to reject people.
Columbia has no idea what the URM status is of individuals it sends waivers to. It is done based solely on LSAT scores. Therefore, though they may have a chance of being admitted, said chance was not Columbia's original intent in sending them the waiver.
Sure they know URM status. That's all part of the LSDAS information I entered when I first signed up w/ LSDAS. I also mentioned the states i'm most interested in attending. And lo and behold, those are the states that send me invitations to apply.
Also, what do all of your "invitation to apply" letters say? Mine always tout how "diverse" the student body is. I mean *REALLY* tout - a big long fat paragraph on the subject. I suspect each school has a "diversity" paragraph they automatically insert into the invitation letters when mailing out to URM's they discovered through LSDAS.
Also, i'm over 30 - which is part of LSDAS info since I had to enter my birthday. I'm sure all of that got passed along as well. Sure, Columbia says "we're highly interested in you and invite you to apply because of your LSAT score". Of course that's BS. Likely, Columbia got all the info from LSDAS and their form letter should actually say
"We see that you're a Mexican-American over 30 with a high GPA in two interesting majors and a 2nd bachelor's degree. Your LSAT is in the toilet. But you do have at least a snowball's chance in hell of being accepted. We know you wouldn't even bother applying otherwise, so here's an app fee waiver. Also, you're very likely to simply not meet our standards, so we will very likely reject you and that will benefit our selectivity rating. But your LSDAS info is mildly interesting (i.e. out of the normal) so we thought we'd give you a chance to strut your stuff."
I think the above probably reflects some of the truth involved in my getting a Columbia fee waiver.