zig does not allow arrays in packed structs/unions specifically for endianness reasons (there may be other reasons as well but endianness is what i know of)

Ah, that is useful to know. Is that documented somewhere? From what I can quickly find in the obvious place [0], the only requirement is that "all fields in a packed union must have the same @bitSizeOf" and [2]u8 does satisfy that requirement.

[0] https://ziglang.org/documentation/0.16.0/#packed-union