So a single man (3 gold) will be able to create out of the blue a 2 silver chevron unit? It only a bit less silly...

I can't really see any good in free experience. Especially not when the AI doesn't get a similar benefit out of it. Why should we get it? Give me a good reason? The survivors have earned their experience, the new men have not.

What people used to do in STW and MTW was to cycle troops back and forth. Jealously saving up those veterans for combining. Even a single Valour was often enough for people to begin saving them. And trust me, it felt good to send in a full unit of quite experienced units when they were created that way.
You didn't have a lot of them. Right now half my troops are silver chevrons, facing green AI troops. And there is actually little I can do about it as I do need retraining, but even with combining there are usually a few units left over. Besides, the system seems to pull the greenest troops into the combining, leaving the best troops in the old unit. Meaning if I combine, I usually end up with a high experience unit to retrain.

So, even if I try to not to use this totally outrageous feature, I can't.