Address sanitizer won’t panic/crash your program on all memory safety violations. Attackers know how to achieve remote code execution in processes running Asan. Asan’s docs specifically call out that you should not use it in prod. In other words, Asan is not memory safe. It’s just a bug finding tool.

Fil-C will panic your program, or give some kind of memory safe outcome (that is of no use to the attacker) in all of the cases that attackers use to achieve remote code execution. In other words, Fil-C is memory safe.

The fact that Fil-C achieves memory safety using runtime checks doesn’t make it any less memory safe. Even rust uses runtime checks (most importantly for array bounds). And, type systems that try to prove safety statically often amount to forcing the programmer to write the checks themselves.