If I said I don't expect a significant delay on a project...

If I said I don't expect a significant delay on a project delivery date 6 months out, that doesn't necessarily mean that I expect a delay. I might know it's getting tight now but I still expect to have it done on time. I might say that I don't expect a significant delay just in case I marginally miss that date.
Also, if they were planning on working a single shift, they could simply add an afternoon shift. I don't know if that was the case but if would make sense if they were not in a rush to coincide construction completion with the Angola national day for the inauguration.