As the title says I was only able to obtain an update for a game (Age of Wonders 3) through Galaxy. Otherwise it was going to require downloading the entire game again.

I've had the game on GOG since v1.704 and the only update available to me via my account is 1.8 to 1.8pbem. Why is a manual update not available on my download list? Is this the case with other games as well? It's very annoying.

My understanding from some threads from a while back is that sometimes updates are available through Galaxy first, and then become available later on the website. Galaxy is supposed to be able to apply patches conveniently, and Galaxy is probably a way to get updates to more people automatically.

Whether patches are available separately from the game is a different matter. I've noticed some people want updates already applied so as to make backups simpler or for some other convenience. And it seems to depends on the operating system, sort of. I mean, I've seen games for download from the GOG website for Windows with several patch/update files to download, but for the Mac or Linux it has already been applied and has only the game file. It's not always that way. (That's not a reference to sometimes when a game just happens to be split into several files that will get pieced together when installed.)

No clue about Age of Wonders 3.

A bit disingenuous. You can still obtain the update without Galaxy, although - as you noted - it requires DLing the entire game again. This is something that I and many others have commented on/complained about many times. GOG says that for some games, due to various factors, this is the best way to do the updates. Sucks, but if you don't want to use Galaxy, that's sometimes what you're stuck with.

*edit* If you contact Support, they can sometimes provide you with the interim patches that you may have missed so you can avoid DLing the entire thing.

Not the answers I was hoping for but good to know nonetheless. Thanks.