Bob Gardner wrote:

According to my SEA Class B chart, if you are at 800 feet and turn before
you get to I-405, you will not enter Class B. Something to check before
takeoff. The Boeing controller has no authority in the SEA Class B. You
should have spoken up before reaching 405.

The airspace there is so complex with not only the Class B but the Renton
Class D. If I were going to land at BFI as an out-of-towner, it would be IFR
or I wouldn't get near any of it. I don't think I would even accept a visual
approach to BFI.