I've had that happen too. After a gravelkind inheritance my brother requested independence with a duchy in my kingdom's de jure borders, I petitioned him to be my vassal and instantly got to defensive pact threat from 0%Yeah, threat seems like a non-issue until you start gobbling up whole kingdoms/empires through inheritance.
Which in itself seems like an odd choice if you ask me.
Expanding through the intended 'slow' intrigue based mechanics (marriage, plotting, inherited & de jure claims etc) should generate far less threat than expanding through lazy holy wars and claim fabrication.
In my current game it seemed really weird that voluntary vassalisation of all the Irish counts immediately upon forming Britannia generated *far* more threat than all of my prior wars of conquest. Perhaps forming Britannia should have generated threat, but after the fact, claiming what's rightfully mine seems completely reasonable and shouldn't worry the emperor of Francia (against whom I have no CB)
This leads into another point; having claims & CBs (as a multiple of realm size) should be what generates threat, not actual expansion.
I suppose you could make the same case that when you declare war you can instantly raise your vassal levies throughout the realm on the same day.Threat is sometimes really stupid. I mean, as Roman Empire (formed with HRE in CKII+), I rapidly had a coalition spanning from the British Island to Mali, from Britanny to Persia including random Pagans and tribal peoples. First, how did they made contact ? The Malian and Russian used their teleporter systems ? And then , how can the Abbassid Empire, the Malian States and Russian tribes could react THAT quickly when I decide to conquer Brest ? By the time they get the news I should have had the time to take over Britanny 3 times !
I mean, I am not necessarily against this feature, but that's ridiculous, really .
I suppose you could make the same case that when you declare war you can instantly raise your vassal levies throughout the realm on the same day.