Wait, you're saying that people claim that they themselves are reptilians? I've only heard the nutters claiming that other people are reptiles. There's always gotta be somebody out there that just has to one up the story.
Your argument is that a brain which is functioning so poorly that it thinks it’s a reptile will be convinced by some piece of paper from a lab? That’s an interesting thought.
There are nice, somewhat tight garments waiting for them. DNA tests are a waste. This if funny farm level delusion, assuming they're not doing it just for kicks. Such beliefs to me are an indicator of a malfunction and just like having your towel with you is an indication of being prepared for everything and that you probably are in the possession of a lot of other useful stuff so is this idea one that comes with a high probability that you have more garbage rolling around in your head.