Yes, that’s weird. If I knew someone would write down every little detail about me, I would be weirded out. I would probably reconsider my friendship with them. Honestly, I would find it creepy.
I’m not sure if you are autistic (this is not meant in a derogatory way) but if it helps you, it’s ok, I guess. Just make sure the other person doesn’t notice it. It can come of as obsessive, creepy and maybe even stalker-like. Especially the speculations.