Harry did not meet the Weasleys on the platform, and while he may have met Ron on the train, it was not in the same way (and, of course, with Draco being more friendly to him already, Draco would no doubt seek him out . . . and if an altercation began, which, Weasley & Malfoy . . . not unlikely, Harry would side with a new friend over random new person, just as he did in canon, if with different results).

If Harry continues being friendly with Draco than even if they aren't antagonistic directly probably Ron won't want to be very friendly with Harry.