It feels a bit egregious when I have to download a 100MB update just because a few characters were buffed or nerfed. More involved changes end up being over 1GB.
Not all versions are made equal either - one might be a character buff, another might reorder assets in the "big huge binary blob file" for performance improvements. At a certain point, rather than downloading 30MB per update for 25 versions, and applying each incrementally (remember that you have to do them in order too), just download the full 1GB once and overwrite the whole whing.
Most backup software is able to do good binary deltas of arbitrary data for decades. Even dumb checkpointing resolves problem of downloading 25 versions - you download latest checkpoint and deltas from there.
Don't excuse poor design and programming, when you know a file structure, creating a differential update should be short task. With a tiny bit of algorithmic knowledge you could even optimize the process to only download needed assets inside of you big binary blob - if the asset was changed 7 times during your last 25 version you only need to download the last one.
It is a complete image, but phones today have nontrivial state that may be a problem - e.g. your baseband processor might have its own rom with its own update protocol, which changed between image 2 and image 7, so image 10 after image 1 will be unable to update the baseband.
I honestly consider that a pretty reasonable trade-off.