The public and the Patreon builds got their own numberings, hence why they seem to be so far apart. The Patreon build gets a new version each month, that's why the number is so high, but it's only a comparitively small update each time. Once a year, Spedumon takes the most recent Patreon build (in this case I think was 0.70), and splits it into three parts, which then become the public builds for this period. In other words, 0.19, 0.20 and 0.21 are the same Patreon update from one particular month, but certain things are blocked off in 0.19 and 0.20, so each new public update from that period reveals a bit more content from Patreon build 0.70 aka public build 0.21. If you wanna know how much further the Patreon release is in comparison, you can check the walkthrough, it always shows what's in the latest Patreon version. If you don't mind to get spoiled, that is.
TL;DR, no, public build 0.19 is not 50 builds behind the Patreon version.