It seems to be a thing for all the incumbent UK banks I've tried. CYBG/B (now the second incarnation of Virgin), Lloyds, Halifax, NatWest -- all have that 3-day delay.
Instant update was the killer feature that swung me to Starling. Well, that and Natwest calling some random guy (who later found me to tell me what happened) for a sales call, only to give him the transaction data for my last five transactions....!
(obFD: no pecuniary interest, just a happy customer)
That's actually the case for my HSBC UK account too. It's impossible to know accurately what the balance of it really is at any time too; both the real balance and the available balance fluctuate wildly with no obvious relation to the transactions, which are delayed by a variable 1-3 days (presumably depending on the type of transaction). They seem to be about ten years behind all the startup banks.