As a Tesco Bank customer a couple of things to note.
Since the breach cash deposits made in store do not appear on the mobile app or web until the following day, they were previously immediately shown.
Likewise some payments now don't show till the following day.
I haven't had chance to confirm if the the available balance is still accurate though it previously was.
I would hazard a guess that they have changed a procedure with regards to processing so they can stop payments or withdrawals. It could also highlight that they were doing something other banks were not as my previous two bank accounts didn't have this ability but I can't comment on other banks.