Yes, but he also wasn't thinking about the four subsequent years in which anti-Brexit forces tried everything they could (and more) to stop the duly passed referendum from actually taking effect. That went a long way toward causing the collapse of Labour's "red wall" in northern England in the 2019 election.
FWIW the trend in the vulnerable 'red wall' seats has been towards the Conservatives for decades. This is partly as a result of partisan and class dealignment, and partly because the Labour-leaning forces of the organised working class have been in retreat there since the 70s. A former mining area like Bolsover, for example, has moved to vote more like similarly situated semi-rural, increasingly elderly, and low-wage areas since the pits closed.
Brexit also a factor in '19, of course, but those seats are red in history and not any more in demographics.
"βIn a 52-48 referendum this would be unfinished business by a long way."
Of course he was thinking of a 52-48 vote for Remain - but his point is still valid.