If that was the case, it would still be discriminatory. Each job should ideally have gender-neutral requirements.
I don't think that is what is happening though. It seems there are different standards for identical jobs.
You can make the case that this unfairness in hiring is for the benefit of gender diversity, but you can't pretend it's not discriminatory. You can argue that the benefits are worth it, or not; that is the only honest argument.
You seem to be conflating a soldier's MOS (or equivalent acronym for the Navy, Air Force, or Marines) with physical requirements.
All soldiers, regardless of gender, must meet a certain set of physical requirements to serve regardless of what their actual job is. For the Army (which I am retired from), this includes being able to qualify on your assigned weapon (usually an M-16, but some are assigned M-249s or M-9s, depending on the weapon complement of the soldier's particular unit), be able to pass a physical fitness test (which, granted, does have different standards for men and women on the pushups and the run, but at least the sit-ups are a single standard now), and be able to carry at least eighty pounds of gear without issue. That has absolutely nothing to do with a soldier's actual job description, which, unless you are in a combat arms MOS, usually does not have many physical requirements attached to it outside of the ones I've already described. Infantry, Armor, Field Artillery, and Air Defense Artillery, the four combat arms branches, often do have some physical requirements involved with the MOS that are unique to that MOS, but again as long as the soldier is able to meet those requirements, there are, currently, no limitations to who can serve in those branches of the Army.
The remaining twelve branches of the Army are either Combat Support or Combat Service Support, which are generally more administrative or logistical, although even there an individual MOS might require more physical capability (being a mechanic, for example); point is, a soldier's MOS often has little to do with the general physical requirements all soldiers in order to serve MUST be able to meet. I don't know as much about the Marines, Navy, or Air Force, but they follow DOD regulations the same as the Army does, and it's a DOD regulation that dictates the physical requirements, so I don't think it's terribly dissimilar.
The long and the short of it is, as long as someone is able to meet the general physical requirements to serve, I don't care if they're male, female, male-to-female, female-to-male, gay, straight, bisexual, or even asexual; they should be allowed to serve their country with the same pride that everyone else who chooses to join the military does. Politicizing the argument, as our idiot in chief has done, has absolutely no benefit for the military and in fact can create unnecessary limitations that will prevent fully capable people from serving if he actually changes policy rather than just tweeting about it. Claiming it saves money is, as has been shown, an incredibly stupid argument when the military still pays for things like Viagra, and spends more on that than they do on transgender surgery. Currently there is no indication that the Joint Chiefs or the SECDEF will be changing the policy without a directive from Trumpy, so at the very least the 15,000-odd transgender members currently serving will not be kicked out any time soon, but I fear that's probably going to happen sooner rather than later, because Trumpy is a knee-jerk reactionist who orders things without thinking about the ultimate consequences. I do hope I'm wrong, though.