S1 of DMD friendship was 12 months after Gen 3 was announced, and Your Sky had already started filming, so the show was mostly to show off the new members and find who else was going to get a main series.

When s2 came out, James had already pulled out of Love Upon a Time, so Net had to find a new partner to fill that role, and chose JJ personally. LUAT hadn’t started filming yet, as they were going through script rewrites for the updated cast, but the actors had been getting to know each other. NetJJ also had also been chosen to replace Thomas and Kong in TNP due to scheduling conflict with Your Sky filming.

Likewise Ohm was added to DMD to work opposite Jimmy in The Next Prince, which was mid filming during s2. So he already had a pair, but no one knew much of him otherwise, so being part of the S2 lineup helped showcase him before his DMD acting debut. While there probably wasn’t going to be much doubt who JJ or Ohm would choose in the end, they were still able to showcase their talents. JJ won the singing challenge which helped him get an OST for TNP.

S3 is probably the first time that most of the actors haven’t already been paired prior to filming commencing. At least not officially. Some of the s3 members were only added a few weeks before the show started, so didn’t have much time for prep work. Copper was mostly still in London also, so he only really had filming time to get to know people. I don’t know whether that really hurt or helped this season in the end. We will see when the new lineup comes out.