The issue isn’t exploding too much, it’s that on a very small sample of them, some of the welding could block the exhaust port that goes to fill the airbag up.
So without that exhaust, the thing just explodes like a small bomb rather than filling the airbag.
The actual number is ridiculously tiny though. They only have less than 10 possible cases across hundreds of millions of airbags over 14 years across the US and Canada.