Keep in mind that Aerospace fighters are not A-10s, more like Space Shuttles with guns.
Yes and no. The A-10 is more aerodynamic than some aerospace fighters and less then others. Mass-wise, base is approx 14.5 tons with 5.5 tons of fuel, and 8 tons of payload, and operationally closer matches a Mechbuster.
Do remember that one hex is 30 meters across. So a BT "strafing" attack might cover a really long stretch of land since it covers multiple hexes. And that BT "strafing" is done with energy weapons only, not with autocannons like a real attack jet might do. Googling some A-10 strafing runs, those are pretty short, though it is hard to judge distances from vids.
Thus, it is plausible that terminology within BTU has evolved, with what now would be called strafing being classed as strikes (single hex attacks), and strafing means something that can be done with energy weapons only.
Indeed. Interestingly enough, it was far easier to strafe in WWII because the primary armament for strafing was the .50 cal machine gun. Ammunition was (relatively) easy to carry, and they fit 2-8 per fighter, and they had a relatively high fire rate. Some of the more strike-focused aircraft like the Il-2 Shturmovik did carry slower-firing cannons which were used to strike vehicles (and were pretty effective against bombers and even fighters when they could hit).
Most modern aircraft can strafe with the weapons they have, the rotary 20mm being quite effective at the task. The A-10 cannot effectively strafe with its 30mm main gun. Even at its slower firing rate (21rps), the weapon generates enough recoil to stall the aircraft if it fires for too long a time. So, they are focused on more strike-style hits with the weapon.
Even with all that, as you said, most modern strafing is not likely to last beyond 30m as it is, which turns back to the strike mechanic. If anyone remembers the Battletech television show with the Banshee strafing, its beams would last long enough for the pilot to spread the damage over the area just by changing angle from strike to ground avoidance. That's the only explanation I can consider as being able to justify it, but I don't know how that works for PPCs and Plasma weaponry.