Aren't high gloss (reflective) surfaces producing caustics rather than directly adding to GI (ambient lighting). At least on first couple of bounces over high gloss, then as "caustics" disperse further (more and more, up to a certain value/threshold?) they start adding to GI.
From observations, such situations can be experienced in shade near large water body areas (seaside, lake, river shore) or on film/photography sets. When sun light hits the reflective water surface at just the right angle (fresnel plays a huge roll here) tiny waves act as concave mirrors/reflectors which concentrate light into beams bouncing into shade and over glossy surfaces which propagate that energy further until "concentrated E" gets dispersed enough, adding to GI. Thus, IMO, there's no need to account bounced light from glossy surfaces with values below 0.03.
BTW (for interested) there's no pure glossy surface in existence.
& We all constantly approximate to certain level of tolerance, optimized for intended tasks.
This "cache" development looks very promising.
PS
Oh, yes i forgot about
convex glossy/reflective surfaces, which directly add to GI because of light/Energy dispersion. Even, if pure glossy surface like mirror.