To be fair, what they actually said was, "Bytes and octets are the same today". It's a little disingenuous, I think, to quote everything but the last word, especially since the qualifier "today" was kind of their entire point.
In the words of SLJ, allow me to retort. Bytes and octets are the same today on the hardware the OP is used to working with; I'm guessing whatever the latest generation of commodity x86 derivatives is.
The real crime here isn't lack of knowledge; it's thinking that one's own narrow experience is all-encompassing and that what's true in one part of the programming world is true everywhere.
I'm not disputing your last statement. I'm saying that, if you are going to quote someone, quote the whole sentence, at least, and don't leave out words that are substantial to the point they are making.
"I wasn't even told that there once were systems where this wasn't true until fairly recently."
Wait, so someone filled in a piece of your ignorance and your response is still "Bytes and octets are the same"?