I don't think the message is misleading, actually. Worded in a way that could (and has been) misinterpreted but there's nothing wrong with the statement itself.
"The active duration of companions summoned with Gysahl Greens has been increased from 30 to 60 minutes."
The change has been made to the companions.
It makes no mention of a change to the properties of Gysahl Greens themselves. The item description says they have an item duration of 30 minutes.
It could be worded better, but the statement as-is does correctly describe the change.