I have never heard that. Just putting it bluntly, Catholics don’t have a concept of “that guy was rude” in Mass — we go for the sake of Almighty God and our own sanctification, and Catholics typically neither know nor care what the other guy does. Catholics tend not to be judgmental about other people’s behavior — everyone is more or less “doing their own thing”.
And I’ve never understood this thing of “leaving right after communion”. You can stay the entire hour to receive, but you can’t manage that last 10 minutes? Are people really that pressed for time? Wait — in the United States, that very well could be. Our entire culture needs to slow down and recollect itself. People are nervous wrecks anymore.
And, as I alluded to above, it’s an American attention span thing. In many (if not most) other cultures, people have a higher tolerance for lengthy explanations. In France and Poland, to use just two examples that are not so far removed from ours (when compared to African or Asian cultures), people take time to go into detail, to consider various aspects, to listen, and to absorb what they discuss. Here, not so much. Everything is sound bites, tweets, texts, and other forms of information conveyed in brief. And I’ve gotten infected with it myself. Occasionally I try to watch the PBS Newshour and the CBC National, and eventually I just throw my hands up, say “this is too much”, and change the channel. Thoughtful discussion and analysis isn’t respected in today’s culture, and this percolates down to inability to appreciate long sermons.