It MUST?
It MUST?
The worst of the worst are those who react before the other person even ended the sentence. Those people themselves most oftenly consider themselves as intelligent, because - in their minds - they already know "everything".
But, sure ... that's not helpful in regards to your post.
The opposite must be true, because otherwise you give room for the idea that thoughtlessness is intelligence. As the depth of thoughts is a function of time, the longer the brain can "analyse and gather", the better the response will be.
The less time spent, the less time the brain has to "analyse and gather", which means that it will bring up whatever matches the patterns first.
It's quite amazing. We're capable of conversing without needing to actually think about what's being said and people aren't even noticing the fact that they're not actually thinking about what's being said.
If you wish to believe that (consciously or not) reducing ones self to pattern matching in conversations equals (any level of higher) intelligence, then I'm not convinced you have any practical experience on the matter.
If someone is able to respond near-automatically and produces an accurate, relevant response that progresses a conversation or situation positively (for whatever that means), then the fact that they haven't spent time and mental energy (and in turn, genuine calorific energy) could be seen as a success.
Now I'm not necessarily arguing that it's good or healthy to have less-thoughtful conversations like that; just that there are other perspectives possible here.
(I think that what really matters is the overall level of progress that humanity can make in terms of achievement - and I think that rapid-response conversations are likely to keep us stuck with existing models of insecure, attention-sapping, user-harmful technology)
Anecdotally, I am one of those people who interject when people are talking to me. I know it's a bad habit, but in most cases I DO think faster than almost everyone I meet, and from my perception people take forever to explain their point. Most of the time I know exactly where they are going on the topic, and I bore easily, so find myself interrupting. It is one of my worst traits, but I challenge that it's because I don't think. I think deeply about everything and anything as I have a constant desire to learn regardless of topic. The down side of this is that most people talk absolute rubbish about topics they know nothing about, yet seem to enjoy doing it, and resent being corrected or educated. I had to learn this the hard way. These days I just don't engage in any general conversations with colleagues or acquaintances for this very reason.