Ah, I see. Smaller bounding boxes are more likely to reach the intended "audience/reviewers". Thanks for clarifying.

So, if I do update in StreetComplete while out walking and online, will they be submitted instantly one by one and create one bounding box per update, or are they still grouped together somehow?

I did not know. I'm a rockie when it comes to mapping. But, this might be a design bug. What I did was installed StreetComplete on my phone, then made updates, but didn't log into my OSM account until days later. So, I might have dumped lots of things at once.

Another thing, that other user already reached out about: I did those edits in Sweden from my memory. I only edited things that I'm 99.99999% certain hasn't changed in the last few months (as they haven't the last 30+ years).

PS. I have no idea what that "bounding box" is about and what it's representing and how it affects the OSM data in the end