"Sibilance as I may erroneously understand it is a lack of transient precision or clarity."
Sibilance is a subjective term so it can vary a bit from person to person. I don't think your statement is wrong, just incomplete. Sibilance (vocal) is when there is an unnatural emphasis on certain sounds when spoken. Words that start off with letters like S, C, K, T are the most common to be effected by sibilance type of distortion. Most people describe the sibilance they hear as harshness that definitely is not natural sounding. If you were to take a recording of someones voice and play it on a system that you hear sibilance on and compare it to what the person actually sounds like in real life, you should not here sibilance. One thing to keep in mind is that sibilance can be caused by any number of things. Things like metal tweeters can enhance it, but sibilance can be on the recording itself. Given that, you can definitely hear it on "soft" sounding gear like tubes and speakers with soft tweeters. You almost have to deal with it on a case by case basis. That's what makes it so frustrating.
"Sibilance as I may erroneously understand it is a lack of transient precision or clarity."
Looking at your definition again, it may make more sense to not say a lack of precision or clarity, but too much precision or clarity. The result being unnatural.
Keep in mind, this is just the way I explain sibilance. No doubt, others will add more to it, and possibly disagree with me on some points. Its subjective.