Apart from the English lessons it makes sense
There are lots of English 4th Gen+ military "avionics"
* terminology which has no direct translation as such. Even speaking English as a native speaker isn't really enough to understand what these specific terms mean when you get into "how" the avionics, weapons etc systems on an F-16 work. Hell I've been doing this professionally for 30+ years and still have to go to "school" just to keep up with how rapidly 4th Gen+ and 5th Gen avionics changes and a lot of 4th Gen+ aircraft (F-16C/Typhoon/Gripen/F-18/F-22/F-35/F-15E etc) initial training is just explaining these what these new terms are to pilots who can already "fly" but haven't yet experienced 4th Gen+ avionics.
As an example, the "unclassified" pilots handbook for a new aircraft like the F-35 etc would be well over 3000 pages long, with the "classified" version nearly doubling that size, and that sort of book would be filled with several hundred new terms, abbreviations, acronyms that the pilots need to not just memorise the term, but understand what avionics function that term carries out, just to be able to "use" the aircraft fully, rather than simply "fly" the aircraft.
A poor equivalency (can't think of a better one) would be dropping someone from the 1980's, whose only driven say a 1986 Ford Escort, into a Tesla Model X Plaid and only giving them a few days training to memorise all of the infotainment settings and functions, after which they have to use every function perfectly or else there's a high chance that they die. I mean both cars have a radio, electric windows and a steering wheel and they're effectively "just a car" so it should be a simple task right?
Thats probably the closest example I can give for the absolute leap these Ukrainians will be undertaking as their Su-27's, and especially their MiG-29's, are still classed as 3rd Gen aircraft for their avionics and the leap to Western 4th Gen+ avionics and its use is a huge one.
* - Avionics from Wiki is "the electronic systems used on aircraft. Avionic systems include communications, navigation, the display and management of multiple systems, and the hundreds of systems that are fitted to aircraft to perform individual functions."