@thewheelie There's no guarantee you'll get an engineer (not everyone speaks the same language, not all team games have every faction's tech available on the same team, not everyone gifts engineers without asking, etc.), and convenience shouldn't be underestimated.
In the team games I've played or seen there's a high correlation between what experimentals someone builds, and what faction they started as (even in games where spawns are close together and the experimental is started fairly late in the game - i.e. scenarios where it wouldn't really delay things if they first asked for an engineer). Similarly T3 shields around bases and high value targets will usually reflect the player's faction, even though sera shields are objectively the best late game.