Both of these are not Annexations. Within the scripts, they change ownership of the regions, control and adjust loyalty. But in both cases, these factions still exist and why you are getting Hannover DOW issue in August 1805.
Annexing is annexing.
AbsorbFaction should be used for both.
FYI, the august 1805 INI script may need to change to reflect Hannover annexation. It currently does a simple adjustment of loyalty.