I would guess they missed the idea that people use muscle memory to close irritating pop-ups without trying to figure out why it's there, or what it relates to. They are then left with 2 send buttons, one with a now ambiguous microphone icon.
Unfortunately, the popup Google chose to use looks like an advertisement. The red "new" banner and animated gif.
They might have reacted differently to an actual dialog at first click that says "This will inject an image into your outbound email, and mute the conversation. Continue?" (with the default choice set to "NO".
It would be cool if websites didn't pop up dialogs for stupid reasons. 90% of dialogs that appear without user interaction are intrusive and unnecessary so users get used to closing them. Would you like to take a survey?, download our mobile app?, full screen ads, and my favorite - "our site has changed dramatically, here's a tutorial."
That's, of course, not what's going to happen.