Is Alex still here?
In another thread in this forum,celebrating the Gallien Krueger class AB amps, someone linked to an interview with Bob Gallien. He says he designed the power supplies to be "not too stiff", ie with small reservoir caps so the amp was deliberately designed to behave as Alex says here. I find that a bit odd.
Sure enough, the schematic shows half as much capacitance as I'd usually expect to see.
These are great sounding, sought-after amps, no-one complains of them lacking weight/heft/loudness.