It was like that over 2 years ago when I went through with family... laptop stayed in hand luggage, and 500ml bottles of water carried through OK, as you say - very welcoming.
OTOH they picked up a small pair of nail scissors in other half's handbag that she had forgotten about, whereas security at LHR outbound didn't detect them.
I don't see how you can hijack a plane with a bottle of water, so it looks like common sense to me to allow people through with drinks that look like they have been bought legitimately for human consumption