Well, that number is 255. Saying it's a (single) byte means you've established the number of bits for it is 8.

No. You've got that backward. At the point the value is returned from pack, it isn't even a number. It is just 8 bits.

They could represent anything, including 8 physically grouped but otherwise unrelated discrete boolean values -- the current on/offness of the headlights, sidelight and tail-lights on a car; yes/no answers to a survey.

Referring to (not interpreting as) that bit pattern using 255/0377/xff is just easier than 0b11111111.

That, to me, is giving the number an interpretation. This observation is very important when it comes to the subject of encoding, especially when we're to print that character (i.e. that number).

Sorry, but you are assuming that the 8-bits represents something to do with "strings & characters and codepoints". It could just as well be 1 byte of a 4 or 8 byte memory address; or part of an IP address; or a sound level ...

The point of my asking the question was trying to make sense of the OP's (of the other thread), description. I knew that I couldn't replicate his apparent scenario on my system, but I am not familiar with the working of Unicode on *nix.

It was conceivable to me that, when running on a "unicode enabled terminal", there might be some default interpretation the byte values printed to that terminal that might be inherited by processes spawned from that terminal.

I am informed that there isn't!

But it was vaguely conceivable that there might be. And that might have been an explanation for the OPs apparent problem.