It has been pretty clearly reported at a number of outlets that the changes in estimates are due to changing factors.Current measures are only expected to redistribute case numbers and deaths (according to the CDC), so I don't even know how he can make that claim. It sounds like and excuse he was forced to make after being pressured by the medical cartel.
25 March 2020
"Neil Ferguson at Imperial College London gave evidence today to the UK’s parliamentary select committee on science and technology as part of an inquiry into the nation’s response to the coronavirus outbreak.
He said that expected increases in National Health Service capacity and ongoing restrictions to people’s movements make him “reasonably confident” the health service can cope when the predicted peak of the epidemic arrives in two or three weeks. UK deaths from the disease are now unlikely to exceed 20,000, he said, and could be much lower."
UK has enough intensive care units for coronavirus, expert predicts