Not sure they play it that ahrd sure they use it 3xb - who wouldn't
But they also have to work these sort of issues to a mutual advantage so they are also able to start their next project on time and still have the windows of "weather" up their sleeves.
If they had to rip the bricks down - which they could have been forced to do -all timelines start to slip until they have some catch up ocurring like a good run of sunshine etc when they'd budgeted for rain.
So throwing in a few extras to sooth the waters - if a much easier / cost effective alternative for them.
Steve