which he called "suppression", was much tamer than the shelter-in-place actually implemented in the UK and many other places. You can see this on page 6 in his paper.

For example, for this scenario he assumed that 25% of universities would remain open, and he didn't assume any closures of businesses, parks, theaters, stadiums, etc. Not really much of a lockdown at all, mostly just school cancellation. This accounts in large part for why the 18 months he initially mentioned are no longer required.