Seems like the other commenters understand this already but it took me a while to figure it out so for anyone else that's confused: IIUC by "natural ordering" they mean you can tell the ordering just by looking at the IDs.
Funnily enough I have the opposite desire - I've worked in a VC system with "natural ordering" and it once led to an incident, where I visually compared two version IDs and said "yep this release has the bug fix". Turns out this is hard to do accurately for big numbers and I was wrong. I put a big warning on our ops documentation saying "never compare version IDs visually" with a link to the postmortem!
Funnily enough I have the opposite desire - I've worked in a VC system with "natural ordering" and it once led to an incident, where I visually compared two version IDs and said "yep this release has the bug fix". Turns out this is hard to do accurately for big numbers and I was wrong. I put a big warning on our ops documentation saying "never compare version IDs visually" with a link to the postmortem!