While I think everyone would agree that things would work much easier if everyone used the same versioning notations and there was an obvious standard, this is no different than saying it would be much easier if there was only one single language spoken on the planet. It would be better if some people didn't use Metric while others use British Imperial as a standard unit set for measurements. It would be best if everyone just thought exactly as I did and never disagreed with anything I said or did.
Even when people agree on the idea of uniformity they frequently disagree on what shape that uniformity should take. When it comes to version numbers, the bottom line is that version numbers are not created/modified for the end consumer. Version numbers are for the benefit/use of the creators. The ONLY reason version numbers are released to consumers is so that when they report back to the creators to file a bug/ask for help/comment on the software in any way the creators can connect that report to a duplicate representation of the state of the software that the consumer is discussing. The fact that most software versioning does have some consistent trends (i.e. increasing in numeric value over time) and that consumers try to determine these trends and make use of them is done at the consumers own risk (of jumping to right or wrong conclusions).
Even if there were a universal standard for versioning (and honestly, in the professional coding realm it is fairly standard and consistent within a few degrees of freedom), that would only go so far in helping the problem mentioned here. The initial question was about versioning not making sense because 0.9 > 0.10. See, we do have a coding standard. And in the versioning portion of the coding standard 0.9 > 0.10 is a false statement. The problem is, even though it IS a standard, your average consumer does not know the standard. It is no different than the average person not knowing about how their refrigerator works or know how the replacement parts are numbered so that they can be found in the warehouse.
One can go online and search for standards on versioning and I'm sure find countless articles. I would be very surprised if it didn't become obvious fairly quickly into reading several of those articles that 0.9 is in fact considered an earlier release than 0.10.
Regardless of the presence or lack there of of a standard, the bigger issue in a community such as this is that most of these games are home-grown products. They aren't being made by a professional studio. They aren't necessarily being made by anyone with any programming knowledge/training/experience. Their only knowledge of versioning is that they see these numbers on other games and they create their own mental understanding of what the numbers mean. How close their assumptions are to actual standards varies greatly. Even those who do come pretty close to an accurate understanding often think that it should be different or that they can "improve" the way it is done. They do this without any research into understanding the reasons of why it is done the way it is done (and therefore fall into the same pitfalls and dead-ends that have been stumbled upon countless times by others in the past).
Standard or not, "home" creators will continue to reinvent the wheel over and over. They don't know there is a standard and they don't see why it matters. They do what works for them. And consumers will continue to misinterpret the standards and read more into what they see than is being claimed.
The main takeaway, as far as the initial comparison of 0.9 and 0.10, is that, even though it is generally referred to as a "version number," it is not, in fact, a single number. Whether "the number" is 1.5, 0.2.6.8, 1200.498.33, or A3G779XJ, it is simply an identification mark. Most of these software identification marks do use numeric numbers and dots (as it makes it easier to make automated code for tracking and organization purposes). Even when they do, they are a list of separate integer numbers, not a single decimal/floating-point number.
It is not, is nine-tenths greater than or less than one-tenth or ten-hundreths. It is, zero compared to zero and nine compared to ten. There is no fractions, no decimals anywhere in a version number.