I've read both messages and I'm still unsure on how fuzzy testing may have not brought up similar edge cases. We literally talking about a parser shutting down

I've read both messages and I'm still unsure on how fuzzy testing may have not brought up similar edge cases. We literally talking about a parser shutting down an entire system rather than reporting malformed data. Considering this is a "one in 15M cases" it seems to me that fuzzy testing would've caught this and probably more bugs in a short time span.