Did someone mess up the numbering format and not format the digit after the . with a leading zero so it’s major.minor/patch-something so 05 and 21 rather than .50 and .21?

I don’t think so, because the 87010 is the build number, which is date-based. This would indicate an S1 build from just before 63.2-88230 (an S2 release for 13.1).

It wouldn’t surprise me if the “factory image” is a newer-than-public S1 build. Factory images are used for hardware testing, so could have new tests added for that. As the app will always “fix” the image before most people can tell, it’s not a problem.

(How did I tell you say? I just took it out of the box, turned it on, connected via Ethernet, and poked around over the network, before getting it anywhere near an app).