It doesn't look like the author knows what Bitcoin is... They state that "Bitcoin transactions usually cost 1-2%" (sic) which is factually incorrect.
I do believe that "there aren't many uses" for blockchains, but this sound more like an inaccurate, unoriginal and badly researched opinion piece.
https://github.com/maxgoedjen/secretive
I've been looking for something like this for 3-4 years but only found it six months ago (in an HN thread). I use separate keys for every use case, and now know every time a key is used for any purpose, whether it's connecting to source control or my text editor is connecting to a remote VM.
Only thing I haven't figured out is how to do git signatures with these sorts of keys, but I haven't debugged it at all.