Whilst I have no doubt of the validity of the ‘absolute maximum’ comment (except in the case of Elaine etc) I think it’s reasonable to point out that very few would approach their manager and complain about overpayment, even fewer to a regulatory authority. Statistics are likely to be skewed towards underpayment, in other words.
The famous BA story/myth? springs to mind where a SYD-AKL-SYD shuttle service was cancelled but the accommodation and allowances continued to be paid. On realising this, enterprising crew were apparently sent from SYD to the hotel in AKL to collect the cash.