First off, BOTS was created by N-Log, not acclaim.
Second, it was just game design. I don't particularly believe there was a reason behind the decisions that they made beyond that they thought it'd make the game fun.
What we can say, however, is that most of the names we're used to weren't the original names they had in development. I believe there was a different name for most things, including bot types between development, BOUT, and BOTS.