ROI from FB ads can only be calculated from tracking conversions on the advertiser's site or in their app. View count alone can never be attributed a ROI as there is no measurable return.
If you pay solely for video views on Facebook or Youtube without any tracking, you're not being a smart advertiser and it doesn't really matter if view counts are more or less correct - you're blindly throwing your money away.
If you do however track your ROI correctly it doesn't really matter how many true view counts you get.
The main problem here is attribution - and with many ad platforms pushing the 'viewthrough conversion' metric, it becomes very messy when hundreds of millions of users start getting tagged as having 'viewed' a video too easily. Future purchases can then be tied back to that 'view', even if it was insignificant in the buying process.
This is where as an advertiser I would be very interested in the distribution of view lengths, to better understand the user's engagement and likelihood that the video made any impact on their behaviours at all.
Although being totally honest, you can't rule out the impact of even a passive 3 second peripheral glimpse of brand video content. Most traditional advertising - TV and outdoor, for example - is not actively viewed, but rather passively 'seen'.
Ultimately it comes back to being pragmatic in the way you assess advertising effectiveness - the promise of digital is perfect ROI analysis and measurement, but the reality is far trickier.
If you pay solely for video views on Facebook or Youtube without any tracking, you're not being a smart advertiser and it doesn't really matter if view counts are more or less correct - you're blindly throwing your money away.
If you do however track your ROI correctly it doesn't really matter how many true view counts you get.