thanks everyone for responding. I would not be surprised to hear of some customers having a no-big-deal reaction to this--it doesn't even raise my blood pressure to close the popup--it's harmless and innocuous. However, if you're feeling a certain disquiet, here might be why: (and feel free to add to my list.)
Setting a precedent: now that Workfront has done it once they'll just assume they have carte blanche to do it all the time (see 2 and 3 below).
Relevancy: we control how we do things-this is what governance is all about. This includes what integrations we use. The decision isn't supposed to be made one user at a time, no matter how innocuous someone else thought the message was. With all the recommendations, webinars, and Leap sessions Workfront has invested in for introducing the concept of governance, this kind of popup could be interpreted as being a little tone-deaf (in my opinion).
Noise:
(waste time and energy) Most users either have an extra keystroke to close the popup, or a keystroke and then they read whatever page they are sent to. Additionally the first time something different happens in a system you use every day there is an "alert" reaction ("is something broken?");
For this specific example, (other) system admins have been contacted by their users and had to field additional communications as a result.
For all of the three above: this is just not how I pictured "mastering modern work" was going to go.
-skye