Who knows, maybe Sunak will surprise us similarly on the election campaign. But probably not.
He's no John Major, that's for sure. The mere idea of the soapbox would probably leave him terrified.
I also struggle to find a proper example of a government running so far behind and turning things around in the actual campaign. If anything there's way too many examples in the opposite direction of entering the death spiral and only making things worse due to panic (Spanish UCD in 83', Canadian PC in 93'). And even if one concedes that Labor underperformed in 97' given the polls before the campaign, it was still a thumping.
Maybe they successfully rally and approach 200 seas instead of apocalypse, but even then seems like a stretch. They seem to have run out of steam, ideas, and anything that's not importing Republican-style cultural war nonsense.