Blocs version 4 is MacOS Mojave (10.14) minimum, however it does run on High Sierra (10.13) and we have some testers working and testing Blocs V4 on that version of Mac OS right now.
So why is Blocs V4 not High Sierra Minimum?
Because we can’t guarantee future versions of Blocs V4 will still run on 10.13. Based on our experience with development, changes in MacOS and our own upgrade cycles, we have set our minimum bar to what we expect it to be in 2/3 years from now.