Certainly a strange move that Apple has just made by releasing the beta version of macOS 10.13.6 for developers without having the final version of macOS 10.13.5 released. Surely in the next few hours the final version 10.13.5 ends up reaching the hands of all users, but at the moment it does not appear and it may not arrive today.
We cannot say that it is something habitual but it sounds to me that this has already happened on another occasion. So far they have been released together with the beta 1 versions of iOS 11.4.1, watchOS 4.3.1 and tvOS 11.4.1. The macOS 10.13.6 first beta is now available on the website for developers.
It is still early to know the news of the new beta version released today, but most of the news is mainly based on the bug fixes and system failures. It doesn't seem like it comes with too many changes beyond what was said, fixes, and troubleshooting from the previous version.
In I'm from Mac, we will be following up on this beta to bring you any relevant news that the developers release, but it does not seem to have much news. It could be that in the next few hours Apple will release the final version of macOS 10.13.5 and we will be attentive to it, but It is also possible that they are already waiting to do it on Monday, during WWDC held in San Francisco. We will see what happens with this final version.