Simply, methamphetamine aren't amphetamines. Similar, but not the same in effect or in capability for addiction, especial since this is pills rather than smoking it
True Methamphetamines are a whole order worse.
30-40 amphetamine tablets a year works out to less than one a week.
Combat soldiers are about 25% of an army. 120 to 160 tablets consumed per year is a bit different.