UV based MWS has disadvantages against certain rocket motor types due to their burning temperature, UV emission wavelength etc. This is one of the reasons why Russian MWS systems sometimes fail against manpads in Ukraine. UV also doesn't detect overall IR signature of the missile which includes excessive heat from drag etc. IR is better at almost everyway. And since MMU is meant for medium to high altitude, using UV MWS is very very bad. And yeah with IR you can have DAS like F35UV-based MWS has higher fidelity on lower altitudes with stronger background IR radiation from the surface. UV based MWS like those on the Belgian F-16s or F-15s acquired by Gulf countries have them for a reason and it is especially useful in dry, hot climates. If Turkish focus is to get MMU prepared against potential low-altitude asymmetric attack near the airfield using something like MANPADS, similar to what those Gulf countries are preparing themselves for, by for example the PKK or Greek spec-ops, a UV MWS could perfectly do its job and would arguably be more suited than the IR-based MWS.
Though since THK's most serious thread is that against the Hellenic Air Force, IR-based MWS would be more suitable for potential high-intensity conflict across the Aegean. Both has its strengths.