Bully tactics.
If it was a genuine ID, he is correct that he would inform Cadent etc. They would visit and, ultimately, cut off in the street if the householder was not co-operative. However, they would attempt to gain entry to satisfy themselves that there is an ID situation and make their own decision. They would not charge in and dig up - and often there is a valve or meter outside the house that they will isolate with.
I have actually been with Nat Grid when we were callled to a definite ID (Flue into a conservatory!). The house owner was intransigent and refused the service guy permission to disconnect. He let us in, but had a vintage motor parked up to the meter in the house which he refused to move for us. The boss was called, he re explained evrything, including the consequence of a street dig up, and eventually the old guy relented, and we capped the boiler. It took a couple of hours.
In the case under discussion, it is a shame the old boy did not dig his heels in, but he probably felt under pressure. Even if it was ID, he would have been in no worse a position than he ended up in.
