With no outs and a runner (R1) on first base, the batter (B1) bunts a fair ball 4-6 feet in front of home plate. The catcher fields the ball but does not throw to first base because B1 is running in fair territory the entire way to first base. The catcher cannot clearly see his first baseman target and the catcher also fears hitting B1 with his throw.

 

After the play, the defensive coach wants runner's-lane interference called (with B1 called out and R1 returned to first base). He claims that a throw is not required in this case... just like a throw is not required by the catcher when the batter interferes with the catcher's attempt to retire a stealing runner.

 

Is the coach correct on either case? What does the umpire do now? Is a runner's-lane violation the plate umpire or the base umpire's call?