Direct supervision means on site. It has never meant on the phone.
This is the most casually broken rule in the trade, and it is broken by schedulers, not by apprentices.
The rule
A plumber's apprentice may learn about and assist with the installation of plumbing under the direct supervision of a licensed plumber. Direct supervision means a licensed plumber is on site during the plumbing work.
Without a licensee present, an apprentice is limited to manual tasks. Digging the trench is fine. Making up the work is not.
Why it gets broken
Never on purpose. It happens when a job runs long, when somebody calls in, when a second service call comes in at 3 PM and the licensed hand is the only one who can take it. The apprentice is capable, the work is simple, and everybody involved makes a reasonable decision that happens to be the wrong one.
Who carries it
The apprentice is the least responsible person in that situation and the most exposed to being told to do it anyway. The licensee and the RMP carry the rule. If you run the schedule, you own this one.
The related thing shops miss
An apprentice who holds an endorsement so he can run certain work with less hand holding also picks up a six hour annual CE requirement with it. Most shops that solved the supervision problem with an endorsement have not budgeted for the hours. That is explained here.
Primary sources
Rules change and this page is dated. Confirm anything that affects your license against the board before you act on it.
Told straight, once
Status: the Texas Plumber CE provider and course applications are with the Texas State Board of Plumbing Examiners. Nothing is for sale until the board issues approval.
One email when a Texas plumbing rule actually moves. One when registration opens. Nothing else.