I think there is a slight hint of truth to the original title, but only a tiny bit. In general (VERY general), I've found that the Japanese are quite open with their emotions in certain situations. Usually this happens in those situations where such a display is encouraged or even expected. Conversely of course, in the day to day happenings of Japanese life, a more measured and patient approach is the norm.
For example salarymen and their drinking parties. At work, its a crisp, starched, efficient place and emotion is expected to not interfere with things. But afterwards, in a setting where alcohol and friendship breakdown workplace barriers, it's almost like a group catharsis where everyone drinks and becomes very emotional, weepy, thankful to their co-workers, passionate, etc. Maybe not at a bar in front of everyone (although that wouldn't be completely taboo) but in a situation such as this men and women may openly cry and display their emotions largely in part to the group validation.
Another example is during the receipt of accolades and rewards on TV. Men and women when they win are often very weepy, emotional, thankful, etc. On a world stage such as the olympics this is not limited to the Japanese of course, but in some lesser situations the Japanese still display an abundance of emotion. Case in point, some of the Pride Bushido fighters, TOUGH AS NAILS, men's men, .. if they win the grand prix or an especially tough fight it's not uncommon to see them cry openly despite being such reserved and stoic guys. This is seen less commonly in, say, American boxing.
If there's any kind of generality to be had here, I'd say that the Japanese spirit of patience and not displaying emotion sometimes results in an abundance of emotion in situations where they're able to finally express themselves.