We discovered during the application of https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2448r2.html (which removes one incorrect example) that there is another incorrect example in dcl.constexpr, Example 2 in (3.4):

constexpr int uninit() {
  struct { int a; } s;
  return s.a;                   // error: uninitialized read of s.a
}

@zygoloid says, "Yeah, it's an uninitialized read, but prior to p2448r2 that was IFNDR and now it's simply valid."