Leaving the country doesn't seem too much of a problem - the 600 people/day cap doesn't apply for departures and several foreign airlines are flying cargo-only flights into EZE which later take off with passengers.
Entering Argentina, though, is a whole different thing. I do not think that this nonsensical measure is done to benefit AR (the arrivals limit also applies to them). I'd rather say that the government, which always lacked a serious Covid strategy, is now completely lost, and this is just something easy to do and sell to the papers.