Yeah that’s an eyebrow raiser. It doesn’t say if it’s Canadian or US cash though. If they had no intent of visiting the US and it was US cash they have some splainin’ to do.
They would have violated Canadian law as well; a dollar to a donyt, they didn’t declare to Canadian authorities when they entered Canada from the UK that they had more than CAD10,000 on them ($10k US equals $13.1k CAD).