My understanding of the med lit is that bipolar and epilepsy aren’t particularly associated, and pure BD in particular is a rarity - when epileptic patients were assessed for BD symptoms, they were mostly only found in the confusional states pre- and post-seizure, which isn’t BD at all.
At least in my hospital, the most common way we get BD patients hospitalized is either during a severe depressive episode, or when their mania results in violence or law-breaking. We do sometimes have patients land on our floor whose first presentation was seizure, but that’s after they’re assessed by neuro and found that it was pseudoseizure (factitious seizure).