https://www.youtube.com/watch?v=8pmvdM7kSzA In this video James said he spars a lot with Mustapha Al Turk, and hard sparring they "really fight", if Mustapha can handle himself with james, Anthony Joshua definitly does.
Eubank Jr never, ever beat Froch up in sparring. Where have you got that from? At best Eubank Jr gave as good as he got, and this was when Froch had just started his sparring sessions.
Sparring is where boxers try things out because it would be a bit stupid to **** about in a real fight, so you will get things like this happening. Also some times, a boxer is just getting back in shape and finding some sharpness early on in sparring whilst the other may be at some kind of peak. Too many variables, you just don't know the full story when it comes to sparring.