I think Drift / Slack does not only depends on the position of the kite. The profile is also very important. C kites have less profile (less grunty kite, less power on the bar) then bow kite. That why C kites won't backstall even whey they sit deep in the ww. This also mean when you edge them very hard in strong wind they will move more forward in the ww and will eat gusty better. But when poping the POP happens to quick and the kite will not move forward so it will just slingshot you toward the kite. this is when you get slack.
i might be wrong though.
You might be right about being wrong
My original post was made after a afternoon drinking session (wind appearance failure), but I'm sober now (well so far today anyway) and thinking about it more, maybe some things are being lost in translation or interpretation?
The slack is caused by the aggressive edging then releasing your edge and pressure on the lines and going towards the kite, the c kite surges forward then once the edge is released falls back to its natural window, this is your slack moment the better you release the better slack, the C kite behaviour helps in its surge then restore behaviour .
I think the C's have a deeper profile, this is what gives them there smaller wind window more base power, less power down. LEI grunt by bar sheeting are cause buy over sheeting and forcing the kite to stall out with a big wind gulp, so to speak which only gives you a spike and can't be maintained, but is easy to do. With more experience and timing a C will exert plenty of power and no lack of grunt -just lack an off switch
Don't agree with less grunty kite either, maybe you ain't been spanked by a C properly.
Don't agree with eat gusty to much either, prefer my rpm to my fuel in gusty stuff, easier on the back, although have ridden some ugly gusts with Fuels over the years and they stand up ok (been riding Fuels since they first made them) so these are observations and my own interpretations, I could be wrong but would need a lot of convincing.