Note: In the begining of the descr_campaign_ai_db.xml it says this..
Additionally, the ai_labels can be tested through event conditions and set through
// a script command, potentially allowing ai behaviour to be changed dynamically in game depending on current game state.
Meaning you can script in a change to a faction's ai_label. An example would be
link_faction_ai england default
which means an AI England would use the ai_label 'default' from that point on. This command dose work, however, in the LTGD log is will still note the faction as using the ai_label given in the descr_strat regardless of what label it is actually using.