It’s the whole deal with player knowledge and character knowledge. Zeke himself has more than enough clues to piece it together and get to that conclusion but I wonder if Kalimat has.
From what I can recall that sentence would be the only connection between the two entities for Kalimat and that’s why I think it would be a stretch for the character to make that leap.
The description Berg gave of “Tulpa” doesn’t match anything Kalimat knows (he also has no reason to connect it to the cthulhu-esque invaders cause even though they might have noticed they were wearing masks they weren’t made aware of what was underneath), and the possible other clues for him would be the tarot cards he drew while talking to the prisoner, which would possibly connect him to the beetles crawling over Utrix or the beetles and armoured constructs Ramus and Berg described but still there is nothing that would justify Kalimat connecting these beetle things to Berg’s passenger.
Again, I might just be missing some clues that Kalimat, not Zeke, is aware of and thus feel it’s natural for him to not jump to any conclusion yet.