Your mason is correct.

Your mason is correct. If and when an inspector "flags it" you can pay the mason to write a report saying the crack isn't effecting structural strength.

Two types of masonry...cracked...and going to crack.

That said, I don't like the lack of any slope on that sill, the grading is questionable, the staining under the window is indicative of saturation of water, and the transition from siding to foundation wall probably allows for some additional capillary wicking.

Thank you, Windows on Washington Ltd. So what is the remedy for that? I think rainwater is tough to alter because the wind blows from the east and therefore blows the rainwater into the concrete.

I would likely seal the concrete with a penetrating sealant that is breathable, slope the window sill, and potentially look at some counter/z-bar flashing for the siding transition.

Grading is handled by moving soils.