[Klathmon]

I believe that was actually the reason why they moved to a "round" configuration.

They realized that the "corner" engines were doing more work, and if one of them failed it caused larger issues than they were expecting.

However in the "round" layout, all of the engines are doing the same amount of work and have a similar amount of control over the rocket, so one failing can be more easily compensated for by the surrounding engines.

[vlasev]

I believe it was not due to this but due to mass savings. The square grid layout uses more material and in a less symmetric way too.