I don't necessarily buy the argument but I am fairly certain that a big chunk of it.
We live in a time where functional electric service is a necessity for life. We also live in a time where extreme weather patterns are getting more frequent and more intense.
The very least Texas could do is implement the equipment and procedures necessary to enable importing power from the national grid in an emergency. The cost to implement interconnects at key locations is infinitesimal compared to the costs incurred when there are systemic outages.
The "we can do it better ourselves" argument only works when you don't repeatedly catastrophically fail at "doing it better."
I'm not letting Texas off the hook -- not winterizing your natural gas pipelines and trying to blame renewables for the grid catastrophically failing is definitely a regulators issue and a return a much money as possible to the investor shareholders without concern to the citizens is the key feature of their system.