Here are contrasting opinions. I side with the "PIGD is real" concept, even if PIGD and tremor-dominant are nodes in a spectrum.
Early after my dx in late 2011 I could walk for miles, do errands in morning and afternoon. All on 3 of 1/2 of 25\100 c\l. Yet even during that time I would lose balance while standing and conversing. I think I've had postural instability from my first awareness of having PD. Little tremor then, only slightly more now.
However, in recent weeks: more drooling, lower lip droops, postural instability has increased dramatically, and I've begun to experience FOG.
Cholinergic herbs help (Bacopa, Ashwagandha, Gingko), but their effect on PIGD/FOG only seems to last ~2 hours, then off time sets in rapidly.