He did not. He said the Haki in Enma is strange and assumed it was because the sword once belonged to Oden. If it was Oden's Haki, he would've outright said it is Oden's Haki instead of calling it strange.
Kaidou realizes that Zoro's sword has strange Haki because it one belongs to Oden.
Kaidou: Hm? The identity of that haki is!!