A (Military) custodial sentence can and does get 'awarded' to Junior Ranks.
If you want to back up a broad, sweeping statement with an equally vague and pointless statement, then you may as well go and work the Daily Mail military news desk.
Admin Discharge statistics for failing the Compulsory Drug Test:
Armed Forces: Drugs: 25 Apr 2013: Hansard Written Answers - TheyWorkForYou
Court Martial results from the military court centres for the last 5 years:
https://www.gov.uk/government/upload...-O.csv/preview
I'll save you some work. Of the 2620 court martial cases, there were 73 involving drugs. There were 4 x Officers in there and one of them was found not guilty.
Of the 73 drug cases, 28 resulted in detention, be that MCTC or prison (it doesn't differentiate). One of those with 120 days was a RN wife. 10 of those detentions did not result in dismissal from HM Service.
The simplicity of the charges presented against the severity of the punishment shows that 'it isn't that simple'. For example, an Army Private was charged with '1 x Possessing a controlled drug with intent to supply' and was imprisoned for 7 years and dismissed. I'd guess that he had done substantially more than just being caught with drugs.
So if you want to keep making broad and sweeping statements, crack on.