Well, since I live in Japan I have some things to add. First of all online gambling isn't really illegal per se. There are always loopholes, otherwise many sites would put Japan on their banned regions list in the TOS. Big poker sites like pokerstars and GG also accept and advertise to players in and from Japan, that's no secret.
Over the years the law changed a bit and got more relaxed. I remember when I came here in 2009 for the first time, back then I informed betfair (worlds biggest betting exchange) that i will go to Japan. As a response they immediately suspended my account (of course they let me withdraw my funds). 7 years later they then accepted players living in Japan, after some law change.

SO yeah, I think the case OP mentioned is only so public because I bet that BIG, and also worked as an affiliate. They don't like people advertising gambling here. But hey, I guess a HUGE pachinko hall close to every bigger train station is no problem.