[Frank Kruse]

Originally Posted by bewk

I think they're the exact same thing, but as you mentioned, it just isn't documented. Ctrl-X still cuts all lanes of automation even if the track is in waveform view.

Not quite. At least not here. ctrl-X will chop away actual audio when you are in waveform view and in that case won't touch any underlying lanes.
If you want it to cut through all lanes and not chop audio you have to have one auto-lane visible, which one doesn't matter. Only then it won't touch your clip and cut through all lanes.

opt-shift-x will always cut all automation regardless of what you're looking at and won't cut clips.

ctrl-x almost feels like something they started programming and then stopped at some point and never finished it (?). It's a pretty odd one. One keypress less though ;-)