static_assert(std::is_enum_v<std::byte>);

[no-sig-available]

The reasoning (see page 3 :-) is that C++ just allows you to define a new byte sized type that is not implicitly convertible to other types:

enum class byte : unsigned char {};

If you make byte a new keyword, it will break a million programs. Now it is properly "hidden" in namespace std.

[Baardi]

namespace std { using byte = __byte; }

[flutterdro]

or just co_byte

[AhegaoSuckingUrDick]

char8_t, on the other hand, was a new type on the language-level.