I feel this is just a cat being a cat. Cats are hardwired to chase any small thing moving quickly. Their eyes are great at detecting contrast, and a bright light has a lot of contrast to interest a cat. They chase it because they don't really understand it's not prey and just a reflection. That the cat lost interest as it got older is perhaps it just being old and less exuberant.

Not this cat. It was an obvious behavioural change from before. Additionally, siblings in the same house didn’t exhibit the behaviour. It got better with old age in the sense the cat started giving up sooner after we hid the light, but there was no loss of energy or other changes.