Nicely avoiding my point which was that the margin of victory has INCREASED since the election of 2017.
By number of votes, yes, marginally.
According to BBC the Labour vote share in 2017 was 48.1%, with Labour having a 1.3% margin over the Conservatives.
This is compared to 31% of the vote in the latest election. (from BBC, where the margin over the Conservatives had increased to 10%, but there was only a 2% margin over Brexit.
So the increase in the numerical margin was likely to be because the opposing vote was split.

You are not comparing like with like. The fact that the Labour vote share dropped noticeably to 31% suggests that they would be stopped dead by 'tactical voting'.