This is almost a "no true scotsman": in practice, a lot of C projects and programmers (even ones that, by most other metrics, would be regarded as professional programmers) do not have the resources to test as extensively as SQLite.
It's more than that, it's a manipulative comment, designed to put others on the defensive about their own skills and muddle the issue.
Any real-world project will be developed unter specific time constraints and have a certain budget. There will be a mix of developers and other roles in the team, with varying skills. There will be politics involved and the project will probably be in use for decades, ensuring that all of the above will significantly change during its lifetime.
Under such conditions, C is an abject failure at supporting robust, quality code, because it neither benefits from a culture of safety (like Ada or even Rust) nor does it have any enforceable safety switches or indeed safety-by-default.
Anything that can be screwed up, will be screwed up over the years by someone, some configuration option, procedure or project management decision. Java is on average significantly safer than C or C++, because no matter what happens, the language won't allow certain errors to happen.
C can be assumed to be a hopeless case, but a purely theoretical way of avoiding these kinds of issues is to have a sufficient supply of bsenftner clones which will supervise a project through its development and operation until it's retired from production (assuming bsenftner is as awesome as they say).
I agree, I'm paid by the hour to deliver a set of features, and the client very, VERY rarely would pay for me to start 'diverging' and writing test cases for something they see as superfluous. A bit of field tests (ie, users as testers) and if it works, it ships.
I don't make the rules. The scary bit is, often, it works just fine; in many cases, it's cheaper to reboot/relaunch for a 1/100000 crashing bug than paying me to find it and fix it!
That's one of the reasons I'm pretty happy to work in a place where my manager will generally agree if I tell them that I'm planning to spend the next 3 months improving the test suite or harness or adding one layer of safety to eliminate a class of bugs or adding a new static analysis.
Of course, this is also a place where we practice static analysis, continuous integration, code reviews and we're now progressively migrating code to Rust.
