No, the OUTSIDE cup is an opaque cup (no holes), INSIDE cup is a transparent cup (holes) lol.. I understand its very complicated, but bare with me!
I don't worry about root rot much, especially with roots excelurator, but its always nice to see whats going on in the root zone, and like you said, its cool too.
I just pour out the old water (including the sludge that would otherwise build up in a hempy rez) from the opaque cup, measure an appropriate dose of water in a spare cup (which gives me the freedom to choose how large my rez is, unlike hempy buckets), and water as usual.
To flush, I simply fill the opaque cup full of RO water, dip the clear cup in, pull it out, all clean Its sort of like ebb & flow. Not saying its for everyone, but if you like a nice clean rez that you have complete control over, its a win.
..One could even put a hole in the opaque cup and treat it exactly as a hempy bucket, except with all the added benefits I've mentioned, if desired.