The intent of changing the penal code was to treat fetuses as people. It was as deliberate ploy by anti-abortion zealots to make abortion illegal by stealth. Just like the campaign to prosecute fetus deaths as additional murders when a pregnant woman is murdered. Well, they got their way in Texas and now we get to see how stupid it is.
But you're right, we all know the intent of the HOV law wasn't to treat fetuses as people. In fact, the vast majority of laws that refer to people aren't meant to apply to fetuses. But in Texas, the law is very clear. Here are the relevant lines from the Texas penal code:
So now, Texas must either amend all their laws intended refer to people, but not fetuses, to clarify that matter. That'll be a shitload of laws. At some point, someone might wonder "Why are we changing all these laws, instead of just reverting the definition change. It's pretty clear the authors of these laws didn't consider a fetus to be a person".