[DohertyBilly]

From the game manual:
5.4.4 Playoff MATCH Format
The Playoff MATCHES take place following the completion of the Qualification MATCHES and the ALLIANCE selection process. Playoff
MATCHES are played as shown in Figure 5 2, ALLIANCE One, ALLIANCE Two, etc. are abbreviate A1, A2, etc.
The higher seeded ALLIANCE will always be assigned to the Red side of the FIELD.

Additionally, ALLIANCE CAPTAINS will always be assigned to the center PLAYER STATION, the first pick will be assigned to the station to their left while they’re facing the FIELD, and the second pick will be assigned to their right while they’re facing the FIELD. If a BACKUP TEAM is in play, they will be assigned to the PLAYER STATION that was assigned to the DRIVE TEAM they’re replacing.

I agree that it would be nice to be able to switch teams around, but it's in the manual, so...

If I had to guess, I would say that is the order the FMS puts teams in when the numbers are entered, so I can see not being allowed to change it once it is established. But if you could chose who went where within, say, 10 mins of selection, it would add some strategy to the process...