I can confirm GBA games mostly use dynamic addresses, especially when it comes to modifying the items and how many of them you have in Gen III of Pokemon, mostly FireRed/Emerald is what I've worked with, however. That's why trying to find a Group offset that modifies what foes you battle in Superstar Saga is a royal pain in the a$$.
Not only that, but the status effects on Mario/Luigi ALSO dynamically alter their location after battle/resetting the game!! <sarcasm>Sounds like lots of fun, doesn't it?!</sarcasm>.