What i think he means is that since "public" is always 1 patch behind, we get the patch notes of the begining of each version, despite having it fully released already.
So from patch 19.1 to 19.X (last one before patch 20) they added a bunch of things, those will show up in the 20's patch notes since 19's patch notes were realesed with patch 19.0 , before they were added.
Since we get the full final version of the patch because it's behind the patreon one, those things that were added mid patch are still found there, but the patch notes are probably not updated to reflect that what's released is not patch 19.0 but the last version of patch 19 before patch 20 .
(If i'm mistaken i dont get it either)