According to this article (by person observing the development of the GAU-8A) this was not a consideration:
Gun studies were performed with some “what if” ammunition designs, but
not much progress could be made in the gun design until the ammunition
design was complete. Trade-off studies for the ammunition included not
only poking a hole through the top of the tank, but established the
accuracy and rate of fire requirements as well. The study was very
comprehensive. Each aircraft sortie was designed for a specific number
of engagements. On each sortie the aircraft would engage the target
for X seconds, at which point Y number of rounds would be fired with
accuracy to assure a kill. Hit and kill probabilities were taken into
account and the gun rate of fire was established at 4,200 shots per
minute. Many believed the system might be more accurate than the
calculations indicated. Should that be the case, the gun system would
be designed so the rate of fire could be halved, thereby doubling the
number of engagements possible on a single sortie.
In other words: the GAU-8A was built to match the specification and main factor in it was lethality (how many rounds to get a kill on target), in turn making accuracy a necessity.
And according to this article the gun's accuracy was very much a factor in selecting the system for the platform:
The GAU-8/A accuracy when installed in the A-10 is rated at 5
miliradans 80 percent meaning that 80 percent of rounds fired will hit
within a cone with an angle of five milliradians; this equates to a
40-foot diameter circle at the weapon's design range of 4,000 feet.
By comparison, the M61 has an 8-milliradian dispersion.
Which means that gun was selected for superior accuracy. Doing everything that's possible to make it as accurate as possible, and then lower it to get a wider spread pattern sounds implausible at the very least.
In my opinion, spread pattern is inherent to the platform and purpose - 40 feet circle at 4000 feet range is, taking into account recoil of the gun and that it is mounted on a plane, rather impressively small.
I'd put that explanation aside, as literally going against the logic, gun spec and design. But that's not to mention the author of that comment was lying. It may have been what she was taught, it's just it's nowhere else to be found.