Taking a look at the existing spaces & load bearing structures in a rocket design and then going with 6 legs is plausible. Walking rockets, not so much.
Rapid reuse is not required to reduce launch costs. Cheap reuse is. If a stage needs to spend x days or even weeks in transfer that should not be that expensive in itself, you "just" need more hardware in rotation.
That said a leg design that can be retracted at will goes a long way to make recovery and refurbish operations simpler and faster.
What I find more interesting is the small footprint of the deployed legs (~1.8x tank diameter) compared to the F9 (~5.6x ?), even smaller(!) than NS (~2x). Blue must be very certain that they can land the stage perpendicular, with very small tipping moments.
Given the offshore recovery plans downrange that makes me think less barge and more Sea Launch style platform. (Land on a platform, transfer on a ship with platform cranes, unload at launch site, repeat.)
How are you calculating landing footprint?
I'm guessing you are circumscribing a circle around the shape of the legs to get the footprint. A better method is to inscribe
a circle within the shape of the legs. That will be your minimum tipover radius. This the primary reason nobody has tried 3 legs, it requires really long legs to get a bigger tipover radius. 6 legs will get you a significantly larger tipover radius for the leg length than a 4 legged design would. That said, 6 legged New Glenn still has a smaller tipover radius than a 4 legged F9
Some math: R=L cos (180/n)
where R=tipover radius, L=leg length, n=# of legs.
As n->infinity, R=L
With one leg not deployed, R=L cos (360/n)
Decide if you require fault tolerance, then optimize for weight. That's how many legs you want.