The Texas State Parks rule about no alcohol comes from the state legislature. Most Texas State Parks Law Enforcement rangers will write you a ticket and confiscate the alcohol the first time they see it. That is simply their job and one which the letter of the law does not permit them any discretion on enforcement.
Do understand that Texas like the NPS, and many other states, has multiple categories of “park ranger”
The law enforcement rangers are licensed and trained police officers. Their duty is to enforce the laws. The majority of rangers are focused on helping those who visit the parks enjoy their visit while protecting the resources of the park from abuse.
When we were TX State Park volunteers- the instructions to us and the non-LE rangers was that if we observed the presence or consumption of alcohol to report that immediately to the law enforcement ranger. And take no other action.
Another point about Texas public campgrounds / parks other than state parks. Many parts of Texas are still legally ‘dry’ with a wide range of confusing variations about where alcohol consumption is allowed/ not allowed.
One COE park that we frequent is under the law enforcement authority of the local city which bans all presence of alcohol at any time in their parks. The local city police will treat any alcohol they see in the COE campground as a serious offense.
My opinion is that if you see such signs in Texas, take them seriously.
At a minimum nothing should be visibly ‘alcohol’. No wine bottles, even covered by paper or a wrapper. Beer should be poured into a cup, not just covering the labels with a coozie.