One other benefit is that because the ad is on a parallax pane, it can resize itself without disrupting the page flow (which AMP does not allow).
I'd love to know what sorts of things you do to avoid accidental clicks. I assume click location relative to the frame of the unit is part of it, and possible pausing to wait for swipe activity to confirm a click, but would really be interested in knowing more (I'm a buy-side ad guy).
Unfortunately, Google isn't the only one with this format, and on many pages I've had false clicks when scrolling through this format. To most users, they will have no clue whether this is a Google ad or not, and I'd be shocked if they didn't equate bad experiences with every network, regardless of whose ad was actually misbehaving.
Our work was mostly related to ensuring that native scrolling of the main page works as expected when the finger touches the ad iframe. This is non-trivial and most implementations do it by forwarding touch events from the ad up to the page, which then feels laggy and leads to touches that are interpreted as clicks.
Overall, I'm curious to see what happens with this. I have my own thoughts on the business side of AMP as it relates to advertisers, publishers, exchanges, DMPs, etc., but from a technical standpoint it is pretty cool what you guys are doing.