I can confirm that I'm seeing the same behavior that @cabreu described: ignored folders don't get synced BUT the dropbox app continues to monitor them anyway and performs some level of processing whenever files are added/removed/edited from inside ignored folders 😩
Unfortunately this all but defeats the purpose of an "ignore" feature for many of us. We need dropbox to truly ignore (i.e. do not react to changes within) certain folders to preserve system resources.