I think they mostly have the stats while they're in, and they drop off after their service, which is where we meet them as characters.
Money can buy you time at the gym,
I'd bear a few things in mind.
The first is that, just taking CT as an example, you can do physical training, improving your Strength, Endurance and Dexterity by 1 each
immediately - but it's not lasting until you've made an 8+ dedication throw after 4 years, and you can't train anything else in that time. Likewise some other things can be improved, again just one at a time, and requiring a dedication throw. It's good now, but will it last?
However, when we look at their career throws, they get 1-4 skill or attribute improvements in a 4 year term, and even some attribute improvements are possible as a mustering out benefit - and no dedication throw is required. Of course, we may take the enlistment or re-enlistment throw as in fact being a dedication throw - was the character a slacker putting in the minimum, or did they work hard and try to improve? In any case if they make it through a term they get some attribute or skill improvements - but in several things. Again, it's good now, but does it last?
From this we get the second idea, that the character may actually have had higher attributes during the career, and even higher skills. The numbers we write down after their mustering out represent what they've retained. Just look at any athlete about 5 years after they've retired from their sporting career - take away being paid to be good, and the superior yelling at them to be good, and their performance craters.
With this in mind, we can think that when we're throwing the dice for attributes and skills, we're coming up with the stuff the character
retains post-service.
Lastly, as I alluded to above, military service is the same as any other job in that it has a significant number of people who bullshitted their way in somehow, who manage to avoid much further testing and find bureaucratic workarounds and sympathetic superiors to let them get away with dismal performance. Many of them become such a headache they're actually promoted to get rid of them.
So I wouldn't sweat the attributes that much.