Sneak does not fade parameters to the current background-state, but to the background state that was active at the time the command was entered.
If the background-values change while the sneak happens (i.e. a Sub is taken from 100 to 50), the parameters fade to the original background-state, then snap to the current background values.
I believe this behaviour was present for a long time.
I'm not shure if it is expected behaviour. If it is, it shouldn't be, as it feels like a bug. Sneaking any time other than 0 should never result in a snap.
