Your rocker panel looks a lot like mine till last year.

Driver side only, driver door only, rear door section was still solid.

Had it cut out and a fresh section welded in. Hence knowing farther back was still fine.

Cost $600, paint and all, well worth it, as I had perforations that wouldn't get better on their own.

Why just that area, I can only assume due to body orientation during parking.

I went the NH Oil route, they shot into frame, doors, tailgate. rocker panels, etc. Pretty cheap at $200 and follow up touch ups are even cheaper. I no longer drive in the salt/winter, so I',m pretty comfortable I've stopped my issues where they stand.