That recipe is authentic Chi Chi's. The author says he worked there 16 years. And I have seen comments by other former employees that verified it. While it may not be an authentic Mexican dish, they are very, very good.
I just doubled the recipe and made the sauce. That's the hardest part for me. It took me an hour, and I can't stand that long without being in a lot of pain. So when I go through the trouble of making it, I make a lot.
Once you get the shrimp and crab meat mixed in, you can cool it and the leftover sauce and freeze it in ziplock bags, and warm it up later in the bag in a saucepan of boiling water, just like chicken ala king

Then all you have to do it put it in the tortillas, cover with sauce, and bake. Makes for a quick and easy dinner.
Better than Bouillon makes a good
lobster base (Amazon link, but you can buy cheaper in stores if you can find it), and for the tortillas I only use Mission brand or La Banderita flour tortillas. Amazon has a really cheap white cooking wine that is very good in this recipe
here.