You have to download the full thing for every major update, yes. The bug fix patches are exactly that, a patch you can apply to a major version with various fixes.
For example you might apply a patch to v0.07.5 Beta to upgrade to v0.07.5 (Public). But you cannot apply that patch to for example v0.07.25 to upgrade it to v0.07.5.
It's simpler than it sounds, because the patches are always clearly labelled e.g. "v0.07.5 (BETA) -> v0.07.5 Patch"
Android always needs to download the entire thing as you cannot make such patches for APKs.