Actually, with the exception of the PCM control software update, what they're saying in the TSB sounds crystal clear to me.well it looks like the fix is an updated part and software update to the PCM/ECU. I'm not sure. The verbage is a little ambiguous
There's nothing to indicated Mazda updated the part (engine oil solenoid). They said the solenoid is getting contaminated and is not functioning properly (sticking), as a result of the contamination, and so they're telling the tech to just replace it with a new, clean one.
Next they say in the TSB that a PCM update was done to 'eliminate the concern'. Now that part isn't totally clear to me, but it sounds like it MIGHT be to somehow recognize the sticking solenoid condition, and compensate to allow the oil pressure to say within spec. Only speculation there on my part.
But IMO the last part about the production process being modified can only be referring to some improvement to their engine/part cleaning. They're focused in this TSB on the root cause of the low oil pressure issue being contamination, and only contamination reduction makes any sense to me for that last sentence