Can confirm, I bought some Panasonic cells roughly 10 years ago for a battery pack, and have ~12 cells that didn't make it into the pack.

They've been sitting unused, in their original packaging, never opened... They're still sitting at the charge they shipped at, but the capacity is so diminished that one can't even run an esp32 for a day. I've tried cycling them to see if I can get the capacity back up, but I think they're toast already.

Yeah, and those come at 3.8V (storage voltage) already, so it's not like they were sitting fully charged.