Some writers write things like Four Fat Harvard Girls Lose Book Bag too. They use sentence fragments. They try to save ink by doing weird shit. Professional Buzzfeed writers write AF (yes, in caps) to mean as fuck. The Atlantic used the words electroöptical and rôles in 1940. Just because some minimum-wage burnout or penny-pinching editor breaks a rule doesn't mean that the rule doesn't exist.
If you go around the office saying that someone drank out of the boss' mug, they'll think you're fresh off the boat. Not only is it wrong in written English, it's not even accepted colloquially in spoken English, anywhere. And so it makes perfect sense that the written form would reflect the pronunciation.
Saying Texas' weather out loud just confuses people into thinking you're using it as an adjective when what you're really doing is trying to sound smart when you're actually sounding dumb. If you point at a book and say, that's Chris', you sound like you have brain damage. How is the book Chris'? Chris is a person, not a book! The only reason that people don't correct you is that they're being polite. And people misspell words all the time and the world doesn't cave in. That doesn't imply any particular thing about English grammar.
Another commenter found that you can say Jeff Bridges' because this is an irregular case to avoid saying the same sound twice—an exception which proves the rule (and also, I don't think it's irrelevant at all to point out the fact that Bridges is literally a plural noun made into a name). But Thomas is decidedly not in this narrow category. His source even uses Thomas' as an example of what not to do, lol. Normally I wouldn't dumpster someone this hard but hn rate limits so I may as well lengthen my response. Nothing personal.
