This article doesn't explain what those digital proofs actually prove. Or to be precise, what kind of attacks they prevent.

AFAICT, it's at least partly timestamping (you can get OpenTimestamps proofs from Woleet). Re: that, I'd suggest reading my OTS announcement blog post which starts by covering what timestamps can and can't prove: https://petertodd.org/2016/opentimestamps-announcement

tl;dr: timestamping is much more limited than people often think, because you can timestamp contradictory things.