I’ve found that herbs like cilantro taste extra strong when unflushed (even I taste the soapy thing, which I don’t normally)
I take my cues from the cannabis hobbyists, and they’ve largely moved away from hydro because of the taste. Unflushed bud is known to be harsh, give a nasty headache, and leave extra salts in the ash for those who smoke it.
I'll see if I can locate the talk from Dr. Bruce Bugbee on flushing.