Good question. In the DSLR world, the interval is exposure inclusive — the 2 seconds is from shutter open to shutter open, so the exposure time plus the write-to-media time must all happen in that interval before the next interval. But some interval meters have an option to "Add exposure to interval". I've never used that option, but since I've noticed it in the past, it occurs to me reading your question that it's possible that the Mavic does this.
So I loaded that same hyperlapse set of DNGs into LRTimelapse (a tool for exposure ramping / smoothing of images for timelapses) because it has an interval field that gives the actual amount of time between exposures, rounded. Below is a screen capture of the first several. As you can see in the "Interval" column, it's pretty much 2 down the line, so the answer is that it's actually a 2 second interval all inclusive. There's the occasional off exposure where rounding brings it to 3, but the next number compensates with a 1 (I'm not going to track down the microsecond differences that caused that) -- that happened only a few times in the total group.
(I must not have had an ND filter on for that one, with the 1/640 shutter speed — time to go reshoot.)
Chris
