Apart from the likelihood that a new Air will bring in more cash than a new Pro, the Air will only need a regular M3 whereas the Pro will need a M3 Ultra (or equivalent). So far, there's been several months between the launch of the M1/M2 and the M1/M2 Pro/Max and another several months between the M1 Pro/Max and M1 Ultra (we don't know if there's going to be a M2 Ultra yet). Since the Mx Pro/Max uses a different die to the regular Mx, and the ultra needs the ultrafusion connector trick to be updated at least part of that is probably genuine development time, not strategy.
Also, if M3==3nm, the M3 Air could easily thrash comparable PC laptops on power/battery life vs. performance, whereas even a M3 Ultra Pro (unless Apple pull something completely new out of the hat) is still going to struggle to match the PCIe bandwidth & RAM capacity of Xeon/Threadripper and the power of discrete, workstation-class GPUs.