These are not "official" new releases.

Basically we apply all the updates from the default repositories and take a snapshot with MX Snapshot. 
This is meant to help new users to test an up-to-date version (with all the bug fixes and security patches 
rolled in). If you already have MX Linux installed you don't need to download this ISO, you get the latest 
fixed and patches from the regular repositories, but if you want to use an up-to-date Live CD, or if you 
want to install on a number of computers an up-to-date version instead of dealing with updating each device 
after the installation, you could download and use this ISO.

Typically, we release a new snapshot on the 15th of the month. If there's no ISO here it probably means there's a newer official release, or there's one in the works.