This is the best example of how bad online translations are without knowing the context. In second sentence it should be translated as "must". As someone mentioned already, driving under neutral sections might damage locomotive, infrastructure and can melt insulators. Just to be clear, there's no need to turn off whole locomotive! Driver only have set throttle (or whatever it's called) to the 0 position. That's it.
IRL and in game these locomotives won't get ETCS mostly because they are, well, too old. In this year Polish Office of Rail Transport said that right now there is around 50% locomotives and EMUs that are 40 years old. So it's not profitable to equip them with ETCS, especially that in Polish railway CA and SHP is mandatory and that won't change any time soon. Route with ETCS is still equipped with SHP anyway so locomotives that don't have ETCS or have it disabled can still drive on these routs. Not to mention that right now main reason to implement ETCS is mostly to run trains with higher speeds (above 160kmph) and to run passenger trains above 130kmph with only one crew (at the moment, a two-man crew is required on the train).
About "working" neutral sections in Simrail. In Options there is "Simulation" section. If possible, it could be option to disable damage from driving under neutral sections for people who want more "relaxing" gameplay 馃槢