Please share the widely agreed criteria to identify code we would all call "unrealistically optimized" ;-) 2 tasks — pidigits & regex-redux — explicitly allow

Please share the widely agreed criteria to identify code we would all call "unrealistically optimized" ;-) 2 tasks — pidigits & regex-redux — explicitly allow use of standard libraries (GMP, PCRE2, RE2) written in other languages. 8 tasks do not. (Those standard libraries were allowed because some language implementations provided arbitrary precision arithmetic or regex by wrapping those standard libraries.) Of course, realistic use of some languages relies on calling standard libraries written in other languages.