tflovik The latest stable version of MATE Desktop is 1.26.0
Ubuntu 22.04 mate-desktop package is also in version 1.26.0
Neofetch uses the command mate-session --version to determine the version of MATE
mate-session is part of mate-session-manager which is also in version 1.26.0. MATE Repository and Ubuntu package
So it is unlikely that Ubuntu (via neofetch or via mate-about) reports MATE Desktop version as 1.26.1 instead of 1.26.0.
This being said the mate desktop environment is composed of many applications (atril, caja, eom, pluma, ...) each of them can have a different minor version number and it is true that there are a 2 MATE packages that have been updated last month and that aren't in the repository yet.
For info here is the way to request package updates on Solus