Your confusion, not mine
The confusion that I was referring to is the difference between being classified administratively as a "deserter", after (approximately) 30 days absence versus being charged, for court-martial, with the crime of desertion.
The crime of desertion has two, essentially independent, aspects: either intent to stay away indefinitely (which is negated by turning oneself in) or intent to avoid hazardous duty. See Article 85 of the UCMJ or the MCM.
On the other hand, after 30 days absence, one's CO is supposed to file the paperwork to change one's administrative status to "deserter". This does not imply that you are being charged with the crime of desertion.
I have personally handled hundreds of cases of GIs who have been absent more than 30 days who have never been charged with desertion (and have been discharged administratively, that is, without court-martial). On the other hand, you could be charged with desertion after an absence of only a few days if the circumstances warranted it: fleeing to another country, for example, or leaving your post in the middle of a battle.
What happens, though, is that a sergeant or CO will call the absentee and say, "If you don't get your >>bleeping<< ass back here by Monday, you'll be a deserter." What that sergeant or CO means is that you'll be administratively classified as a deserter, not that you'll be charged with the crime of desertion.
Susan