I think Kolevatov is quite an outsider in the group.
He's only been hiking with Dyatlov once, and once with Blinov, when the others were quite more used to hike together and for some, good friends.
Plus, he had been working earlier in his life. Ha was probably not "the standard student" in a matter of maturity. (Dubinina herself is saying some of the guys are quite more mature than herself.) Zina is young, she can feel a shift between them (not that everybody will, some guys are probably closer to him than to her in a maturity matter.)
He is probably ambitious, very ambitious (enough to leave a very good job in Moscow to get a better, more secure one later.), or he has something to hide witch motivated his decision: in any case, not the "standard student" here neither.
He don't seems very involved in the hiking club : his list of known hike is not long. I think the New Year hike he did with Dyatlov was a test after he asked to enter the Ortoten trek. His mother said he had to pay/provide most equipment until he "ran out of money" (probably not quite, but still). So he probably earned his place in the trek that way.
For me, there is nothing here but a comment about Kolevatov's trait, and not important enough to make the "probable quarrel" neither a fact or a matter of life. But who knows, Kolevatov is so mysterious !