I have never heard of an idea that because one ii learning Torah, that he is not obligated in some commandment. From where the idea comes from that because some people learn  Torah all the time, therefore they have no responsibility to guard their own lives.  Rather I think this is a smoke screen. The religious simply despise  fry yidden [secular Jews] and would rather see them die, than to serve in the IDF.    it would be different if at least they would be honest. Let them just say they refuse to be anywhere near fry yidden because [according to them] they are all apikorsim/heretics. At least they would be honest. But to lie about what the Torah holds is the most despicable thing to do. That is one of the things that one has no portion in the next world מורה שלא כהלכה to lie about what the Torah holds on purpose.

the above paragraph was written not in an academic style, but for now let me add that i am aware that one who learns torah all the time is not obligated in the three daily prayers, and that in general there is an over arching principle one who is involved in one mitzvah is not obligated in another. however this later  principle only applies to Torah when there is someone else that can do the mitzvah. And in fact I think many people that were learning Torah thought privately that that is the reason  they decided not togo into the Israeli Defense Force. 

there is a ort of problem with pride- that the religious believe they are morally superior to fry yidden. that of course  absurd by reason of how we see them act every single day.