All soldiers undergo basic training. Basics of infantry because everyone is considered first and foremost infantry. After that you're trained in your selected job position. For the Army this is AIT (Advanced Individual Training), your AIT is based on the job you took (MOS). I was initially a 13M, I shot rockets out of a tracked vehicle called MLRS. I then reclassed to Unit Supply (92Y) for a myriad of personal reasons.
Your selected MOS puts you in specific training to do that job. A wheel vehicle mechanic knows different things than a track vehicle mechanic. So even positions that seem on paper closely related can have wildly different training. This makes it hard to simply swap people without retraining which is a massive cost.
Unit supply is trained on different regulations than the IT people running even though they're often side by side at headquarters. Different processes, papers, and regulations for different paper pushing jobs. "paper pushing" jobs are often not trained in advanced warfighting operations like clearing villages vs clearing singular rooms shown in basic training. Or operating heavier weaponry vs just what you get during US weapons training in basic.
But ultimately everyone is (in a perfect world situation) deployable... even the totally not combat related chef (Culinary Specialist 92G) gets deployed to warzones because soldiers need to be fed. Do you want to disadvantage the guy working a non-combat job in a warzone in case the FOB or base gets bombed/gassed?
It's kind of a fucked position to say that anyone at any time can be deployed... but this specific group will be at a much higher risk of dying because a physical condition can't be accommodated for reasonably... But you're going anyway!
The alternative is to say a specific group can't be deployed because of the a condition and thus they get to fill stateside slots permanently which now affects everyone else quite negatively as they will need to deploy more often.
There is no "win" here, nor reasonable equity to be had without accepting that people will die because of the position. Now, personally, I'm in the position where I want to see less of my people die wherever possible... In this case the only answer that makes sense is to not put them in dangers way from the get-go, but that makes them unemployable... which ultimately means they shouldn't be in service at all. Which sucks as a position. But I don't see an alternative answer.
And to make a note... The article is specifically referencing Marines... They're a much more extreme version of this... Even the logistics/operational MOS is trained to be infantry first and foremost and expected to maintain infantry readiness much more so than other branches of the military. In the Army, most non-combat positions are expected to lose a lot of combat effectiveness over time as they train those skills much less.
Edit: I guess TL;DR, we don't build units to be non-deployable as that's counter to the job/point of the military... And we don't get to pick and choose what the enemy attacks. My FOB was attacked a bunch (mortared at least every other day), and we weren't near anything that I would consider "front lines".
Don't thank me... Thank my recruiter.