I've pulled a ton of L28 pistons that look like that including a 280zx that never experienced boost.
I've never seen this in an engine in florida (though it could happen) but have seen many in cold climates like virginia in the winter.
What I find knocks the skirts off on L28s is high revs at low temps.
On my car that lost all six, it ran fine, had no blow-by and only made slight knocks when cold. I only found it when going in to fit new rod bearings in prep, for a turbo.
If you have a thermostat stick open or don't run one in sub freezing climates, you can run the car down the highway as many miles you want, pull over at a rest stop, and feel the side of the engine is unbelievably cold for an engine you just ran hard.