I never disconnect the negative battery terminal unless it's absolutely necessary, which it almost never is. It's a stupid request. If I feel it's necessary, I will pull fuse(s). I own a factory service manual on my car and know which fuses to pull if need be. I think people are sometimes too lazy to do their homework to look up the appropriate fuses.
If it matters, and in this case it does a little. I'm even less likely to remove the negative battery cable on my side post battery because side posts are prone to breakage.