A lot of CAS is not pre planned. The thing with SF is the S. If they have a mission coming up that with a known time and date that fits into the ATO then often they can get an air unit allocated and this get a tailored load. or they may have their own organic air support allocated at all times (rotary - they won't get fixed wing in that way). A regular army platoon going on a patrol is unlikely to have that pull.
Regardless of who you are however if I it is short notice, reactive cas like a call to a tic from ground alert, the guys on the ground have to take what they can get, both in terms of platform and weapons.
How Afghanistan Distorted Close Air Support and Why it Matters
i don't doubt your colleague in what he said. I'd be surprised if it is still the same ratio the current fight, it's a different war.
The very thing that makes a heavy useful in situations (size, which then gives them great endurance and loadout and often superior comm) is also a compromise in that they requires significant airspace, they generally sit further from the target area with a longer run in to attack and greater egress time. There is also the fact that they don't work as a pair so are naturally disadvantaged when it comes to maintaining PID/tracking movers/searching for targets etc as they have 1/2 the number of pods.