Ann: Minbos to Pursue Yellow Phosphorus Potential in Stage 2, page-327

Maybe they had a conservative timeline for construction to play it safe and they believe they can make up for the lost time to date. It might also suggest they are very close to signing the EPCM and getting into construction at full speed without further delay.
On the first point, it's quite possible they were giving themselves an easy and conservative timeline for construction so that the inauguration ribbon cutting ceremony would fall on the 11th of November - Angola's national day. I know it's a big deal politically to cut the ribbon on that day. Not much point finishing a month earlier and having it sit idle.