But "undefined ops" are not part of the "8080 instruction set"; supporting those would be "binary compatible with the 8080 silicon".
The parity flag is a breaker though; "binary compatible for code only relying on the 8080 instruction set, other than values of the parity flag".
By the same thinking that have the parent post The 80286 and 80386 aren't binary compatible with the 8086. Because they replaced undefined opcodes with new stuff.