They've made some changes so that they can send their military elsewhere in the world now. But it is still rather limited to its actual implementation. UN peacekeeping missions, defending allies when the need arises, etc.

I think Japan joining the conversation is just sending a message to Russia/China that the NATO framework is absolutely larger than just Europe and that the 4 pacific nations (Australia, South Korea, Japan, and New Zealand) who ally with the West are fully integrated into the larger global defense framework centered around Washington.

Japan's domestic politics is super against the military being used abroad, but the government faces all sorts of diplomatic pressure from the USA. Which, given China's recent ambitions in the rest of Asia, Japan can't exactly take Western-aligned defense framework for granted.