Honestly, this sounds like an interaction between someone who feels like when he opens up his partner finds it annoying. . I Love talking, and have found that around talkative people I talk lot and relax, around non talkative people I can drive communication sometimes but can feel very watched, disapproved of and freakish around non talkative or introvert people.
The horrible thing is that if you are wondering if he is bipolar, you aren't genuinely connecting with him in conversation, he will sense that and this will depress him.
My sister was diagnosed with bipolar and if she got angry, she was ignored, if she was talkative people would stop her mid flow and make her feel like she should shut up, and her boyfriends family would treat every thing she said as ridiculous, so she could never just be. She became her 'disease', but I work in management, and people pretty much always become whatever expectations you place on them.
A friend of mine thinks ks of himself as normal, but he's an uncommunicative silent person, if I meet him for a drink, there's no input from him, so I just talk away. Recently he has read something about bipolar and thinks I have racing thoughts and uninterrupted speech. I do, because he is boring. Around chatty interactive people I'm normal.
I have another friend who is normal, but alcoholic. Diagnosed as bipolar because he gets hangovers, but tells his psychiatrist he has regular cycling depressive episodes.. But doesn't tell him he drinks to oblivion 1-2 days before his depression/disconnected thoughts.
I went round to his after a really brilliant day at work, and looking and he hold, my upbeat chatting ss had been relayed to everyone as 'like me when I am manic' so everyone connected with him started interacting differently with me because of my 'episode'
It's very dangerous to watch and diagnose moods and periods of feeling yourself v periods of work, stress or worry, and labelling them disorders.
It's more of a disorder to expect everyone to stay in one mood all the time or be caregirised as mental. That's just sinister