Since I'm meant to be working at the moment, I won't read the full article right now, but I assume in the accelerated scenario the vaccinations are being administered more swiftly, and the deaths estimate therefore goes down.
Fairy Nuff, I just did and it relies on an estimate of 500,000 vaccinations a day rising to 600,000 a day by March - optimistic.
On the 37.000 or 40.000 as totals for the numbers of Covid deaths in 2021 - given that the UK has already recorded 20,000 these also seem optimistic.