-fsanitize=object-size reports out-of-bounds access as misaligned access

[davidben]

If building the following with -fsanitize=object-size, the sanitizer correctly flags the code as UB...

#include <stddef.h>

void ReadValueOutOfArrayBoundsRight(char *ptr, size_t size) {
  char c = ptr[size + 1];
}

int main() {
  char foo[16];
  ReadValueOutOfArrayBoundsRight(foo, 16);
}

https://godbolt.org/z/e4oWfYdPG

However, the error it outputs is:

/app/example.cpp:4:12: runtime error: load of misaligned address 0x7ffcd4609ba1 for type 'char', which requires 2 byte alignment

This does not make sense because char does not require 2 byte alignment, and indeed the alignment is just fine. It's just out of bounds.