There is no real reason for them to follow the normal version numbering system, if they prefer a more “solid” numbering system there is really nothing wrong with that. We shouldn’t be so dubious of business tactics that we outright fear every decision as a way to “get us.”
What you have to understand here is that Unreal Engine 4 is probably the only SaaS model I’ve ever seen that allows you to keep the last version you paid for if you stop subscribing. What they do use to keep us subscribing is a constant release strategy, which is part of the Agile Development approach (as opposed to a Waterfall methodology). This is not only good for Epic, but really good for us, because it keeps them working on the engine constantly, gets releases pushed out before the tech becomes obsolete, and allows them to quickly update the tech that does become obsolete. It not only keeps the engine on the cutting edge, but it also allows for better stability as it is easier and more efficient to have QA teams work to debug individual small releases, then to have them go through a massive release with even more bugs all at once. Now, this methodology can sometimes force releases too early and thus results in a less polished/debugged release, but what usually results is many well polished small releases with only a few that were a bit rushed, as opposed to a few massive releases which are often bugged, and then either a series of small patches or a very long wait for a new version that fixes those bugs. It’s worth noting that very few companies with shorter OR longer release cycles even do half as good as Epic.
Finally, consider that it is easier to tell someone “Hey we’re getting a pre-built water blueprint in 4.7!” then to say “Hey we’re getting a pre-built water blueprint in 4.007” or even “4.6.2”