Is bipolar with multiple cycles in a day (ultradian cycling) actually bipolar?

I've read some lay accounts from people who claim to have a sort of ultra-ultra-ultra rapid cycling (ultradian) version of bipolar I, where they reportedly cycle multiple times in single day, but I've also heard that these types of "cycles" can be better explained by emotional regulation deficits, such as those seen in borderline personality disorder, and thus aren't indicative of true bipolar disorder. A quick pubmed search reveals relatively little literature on ultradian bipolar cycling,... Is bipolar with multiple cycles in a day (ultradian cycling) actually bipolar?
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