Feedback generates mod power for summon mods via the 20% single charge cost component, but does not generate any mod power from damage dealt by these mods.
Repro: Equip feedback and familiar/rootlash. Cast the mod away from any targets and note the amount regenerated. Then cast the mod near targets (dummies are fine) and note that the amount regenerated is no different.
This is probably related to the bug where summon mods do not benefit from failsafe/harmonizer/pressure point, which I am reporting separately.