It is if you run your water through the attic instead of the ground.
You need to heat/insulate/otherwise monitor/protect it from freezing.
For my run, the “repair” tee is in the garage (no climate controls) on an exterior wall (minimal insulation, being part of an uncontrolled area) and then about 10’ through the attic above said space. Poor insulation (I suspect) is the culprit, and it HAS frozen, though without bursting the PEX (thankfully). Now that I know, I can plan, and have had no problems since. But that first freezing evening was a royal PITA. I am fully convinced that just letting it happen every time would hasten the destruction of my PEX, which is not all that resilient to repetitive flex. I also think in Texas this can actually be WORSE than in a northern climate, because we only freeze for a day or 2 here, usually, so you’d get several heat/thaw cycles annually, unlike the great white north where it usually goes below freezing for the winter, and then thaws come spring.