Bug: direct time for a intensity change not working as expected.

Correct syntax: Chan x+y @ Full Sneak 10 Enter

Why is it "Sneak 10"? Ive been told sneak is to go the inital state of the cue and not to a new one.
Why does Chan x +y @ full time 0:10 immediately go to full instead of (if it is the wrong syntax) doing nothing and reporting an error?

you've been told wrong or rather you've been told unprecisely. Sneak is to do something slowly. if you use it without a target it will make the channel go back to its background value in the time you've specified (or the setup time).
if used with a target it goes there in the time you specified (or the setup time).

the syntax function correctly, it might just not be what you expect it to do. you're telling the console to set a level and to give this channel a discrete fade time. and that's what it does. no need for an error to pop up.