"Marcus et Stephanus in colloquium veniunt"
Latin: "Marcus et Stephanus in colloquium veniunt" Translation: "Marcus and Stephanus have a conversation"
I'm not sure how you just drew that conclusion from what I said.
Plenty of authors used it, Nepos, Cicero, Caesar. It appears often.
'In + colloquium/conloquium + ven-' appears only 15 times, by my count, in the whole classical corpus, and, as far as I can see, just about always in a context such as a parley/conference/negotiation with a general or king or similar about a subject such as war or peace. I see no instance of it anywhere that suggests it is a natural way of describing two regular people just having a conversation. It seems to be in quite the wrong register, and so a little absurd in this context -- like if I were to describe you and I now not as 'talking' but 'entering talks'. I would call it administrative language.
We could instead say that these two chaps 'colloquuntur' or 'sermonem conferunt, serunt, caedunt' or 'confabulantur' or 'sermocinantur'. Some of these expressions are uncommon, but a simple 'colloquuntur' certainly is not.
That sentence accepts a lot of alternatives:
Marcus et Stephanus colloquuntur.
Marcus Stephanusque colloquuntur.
Those are just two of the 21 versions the other contributors added.
There is no context in the sentence to suggest what register we should use. When the team wrote the sentence, they decided to include phrases and structures from authentic Latin. They also added simple versions to reduce false wrongs.