Artemis Vengeful assault not giving proper attack speed

[Palamnaeuss]

Activating skill adds 65% attack speed buff for 5 secs. If you don't hit god it works as intended, for 5 secs.
After hitting god 4 times the buff gets extended but attack speed buff instantly gets down to like 20%.
Is this intended? It's kinda strange that after activating skill, and you have e.g. 2 attack speed, you will hit god 4 times in 2 secs, so you lose 3 secs of 65% increased attack speed.
I am fine that extended buff can be lower than 65%, but it should happen after initial 5 secs.