That wasn't the term he used at all.
He said
"
The decline in January was almost certainly because of the Christmas period, being as people were staying at home more. Although there were concerns that Christmas may drive the epidemic, the evidence is that Christmas probably reduced the epidemic. Because people were at home, they weren't going out to work. Schools were closed and, since then, case numbers have dropped far more rapidly than I was expecting with this new variant. This is driving my optimism".
The point you are referring to is at around the 17 minute mark on this link.
https://www.bbc.co.uk/sounds/play/m000rvp7