Mutton has been a normal food in many times and places. It happens to be out of fashion in most of the English-speaking world right now.
I grew up around sheep and often ate mutton as a child. To me, calling young mutton “lamb” has unpleasant connotations. It would be like calling the meat of a relatively young pig “piglet”, or the meat of a relatively young chicken “chick”.
The reason for this is that mutton is supposed to smell a bit funny, and lamb doesn't.
In any case, you can get some really tasty lamb dishes down under (e.g. my Mum's slow roasted lamb shanks).
burp
You mean, it would be like calling something what it is, rather than using a euphemism to shield yourself from what you're doing?
Regardless of your opinion on eating meat, I don’t think this is a failure of euphemism so much as an accidental dysphemism.