1. He’s a vastly more senior person than a cashier.

2. It’s not the lack of understanding that’s concerning. It’s the confident wrongness.

I wouldn't expect the cashier to be selling me a product they didn't understand either. If my bank tried to sell me a new security because it was backed by custom chips running HTML, I would probably switch banks as well.

Lying with confidence is, after all, where the "con" in con man comes from.