The three event test certainly wasn't an indicator of how fit you were to fight. I knew guys who couldn't bench press 120 lbs or hump a 100 lb ruck more than a couple of clicks, but they could max a PT test almost effortlessly.
True. It is by no means perfect, or close. Its real advantage is that is costs nothing and can be done almost anywhere.
I think PT tests should be MOS (Military Occupational Specialty) specific, geared toward those tasks a soldier needs to be able to accomplish to perform his duties. There would of course be some commonality and overlap, but a clerk typist does not have the same physical demands as an Infantryman. A wheeled vehicle mechanic does not have the same physical demands as a cannon $#@!er. A Blackhawk pilot does not have the same physical demands as a combat medic.
Unless its changed Marines, Army all the branchs all trained for combat first, then went to their specialty, clerk, whatever. The premise was at any time any soldier could be called to combat to defend their country, that may have changed