It's pretty frustrating in OM too, especially since the download usually fails after some time (my guess is phone goes into some power saving mode and kills the app, which it shouldn't do, but still).
I think closer to the end of last year they have released map updates roughly weekly or bi-weekly. Well, took me roughly that amount of time to update the map, so it would be downloading basically all the time, and the solution was to go to my friend's place, who actually has decent internet connection, and even then, I would have to restart the download 2-3 times.
Oh, and if the download fails and you don't push the "retry all" button, or something, you have to __manually__ tap all the tens or maybe hundreds of sub-regions which have failed, since you can't download all of them for a country with one button press after at least one succeeds.
Also, OSM uses git-like system under the hood, I guess, it's not possible to incrementally update the map since they re-package it as some kind of binary blob of sorts, but still, incremental updates would be nice.
Overall, not sure if Google maps is better or worse for this, but this is frustrating enough IMO.
Source: https://support.google.com/maps/answer/6291838
That might not be a problem in many cases, but at least Organic Maps doesn’t seem to have this limitation.