In all honesty if I wasn't talking about knitting then yeah, size could equal length... like in the diy store and they ask you what size do you want, you could say I need a 4ft long piece, etc.
But in knitting, I think they would also equate size with needle size not length.
It's an interesting ole' thing this language of ours. Through blogging I also have friends in Australia and South Africa and we can easily catch each other out, or have them say "I have absolutely no idea what you just said"!
I would have also taken hydro to mean something with water too!! Dang Canucks! Sure she's not French Canadian!!