I first noticed the thunder buff being weird when testing the monster: It that Stalks, which is essentially a copy of the Pale Seraphim.

Theory: Since the PoeDB page was recently updated, and usually is just direct automatic datamining from the client, I believe this was a change made with the introduction of keepers and the monster: It That Stalks. But I can not confirm this, and we summoners might have been debuffing ourselves this whole time(Yikes).

Main Character raw PoB: https://pobb.in/jWaIUfZC4m_m

Target Dummy raw PoB: https://pobb.in/LLgRixbHKkot

This video was recorded in patch 3.27.

00:00 Baseline Test

00:14 With Thunder Web

00:48 Action Speed Increase

01:02 Monsters

01:26 In Short