The problem you have with the DPS is they are covering their rears by not committing to say "Oh, it's this' or 'Oh, it's that'. They will not give a legal opinion on the enforcement of a statute and will play the gray area. Unfortunately that translates to those (i.e. student instructors) who don't understand they are teaching you what the statute says, but not how to interpret the law, incorrectly and thus the student instructors come out of the certification class misinterpreting what they are saying.
A good example is enforcement of a 30.06. I understand that one of the last classes was told that any 'no guns' sign is notification of the owners intent. Well, yeah, it is. However, it it not LEGAL notification that meets the requirements of the 30.06 statute and some student instructors said DPS was telling them that any 'no guns' sign was valid. What the DPS was apparently trying to infer is that if you pass a non -30.06 'no guns' sign, that you COULD be arrested and charged if someone wants to make a test case out of you. However, in their attempt to not give legal advice they don't get the real message across to the students that 30.06 is the law, and all other signs are not, but it may take a trial to prove your innocence if some eager beaver DA wants to play and challenge you on a non-30.06 being valid notification. An example of that is Grapevine PD saying they believe the non-conforming signs on Grapevine Mills Mall are valid and they MAY arrest you if caught carrying there.
So, unfortunately, unless the instructor has some legal background, is smarter than the average bear, or joins the Texas CHL Forum and gets the straight dope, then they go off and incorrectly teach their students the law.