It is headlines like this that shows the media have no understanding of boundary changes. A 15% Labour lead is a swing of 13.5% from Con to Lab, which on the current boundaries would result in a Labour majority of 26, but we all know that in 1997 Labour went into the election with a 18% swing and came out with a national swing of 10%, therefore are the I running this story to scare Sunak or to show that they are on the verge of supporting Labour?
Even assuming the former figure is actually correct*, polling then was mostly rather different to now - and even if it wasn't, something happening once does not mean it inevitably will again.
(*which I'm pretty sure it isn't tbh - maybe the *best* polls for Labour were saying that at the time)