WHBM
The implication of the statement is that the Airline knew full well before departure that the flight was to be diverted and chose not to inform the passengers until it was too late for them to make alternative travel arrangements if necessary.
Missed connections
Taxis, family, friends meeting them at the wrong airport etc.
Had the customers known in advance of the change they would have been able to mitigate against the consequences of the delay/diversion.
Lastly if this assumption is correct, this is just plain dishonest and no doubt done to prevent complaints prior to departure and to avoid cancelled tickets or other associated costs.
Such a cavalier attitude to customers appears to be endemic in modern management and quite rightly should be open to challenge by those who receive a service that is not as described on the ticket that they have paid for.