That has a lot to do with they way it's cooked and how mature the animal was.

I've eaten mutton in the US, in China, in India, in Afghanistan, in Pakistan, in Iran, in Iraq, in Turkey, in Greece… I think your theory doesn't stand up to scrutiny.

Edit: downvoted why?

I don't eat mutton regularly, but when I do I can notice the difference between mutton and lamb.

Last time I've eaten, like a month ago, we asked the waiter what was the difference between two plates and she told us basically that, one was more tender with a light flavour, the other one was stronger.

Just so you know. I did not downvote you.

India, Pakistan called goat meat as mutton.

Yes, still tastes bad to me (I admit this is subjective).