Eh, if you really want to get serious about it, it absolutely can be dissociating. But really, it's just a meme, and it's here for laughs.
Edit: I don't know why you are downvoting me... #2 question from the Dissociative Experiences Scale, which is used to measure dissociation: "Some people find that sometimes they are listening to someone talk and they suddenly realize that they did not hear part or all of what was said. Select the number to show what percentage of the time this happens to you"
Dissociation can absolutely be tuning out during a conversation, it's all about WHY it's happening. I'm a therapist who specializes in trauma and dissociation... and I'm honestly not sure why this is a controversial fact.