Takata also makes different types of inflators, and cars often have different types of inflators in them at the same time, and all of these airbag recalls have been on specific inflators made at specific times or specific lots that were known to be problematic. Some were also only recalled when the vehicle was sold or operated in humid areas.

I had a vehicle that was recalled once for the driver side airbag, and then later called back for a recall on the passenger side airbag. IIRC some cars early on were even recalled for the same inflator twice when it was found that the replacement inflator had issues.

There's all kinds of details in the weeds here.