Warner Music Singapore was not responsible for the fiasco that happened with the 20th Anniversary tour. In fact, I think they've got zero involvement with the tour in the first place. They were just involved in distributing releases from avex's Japanese artists. It was the conflict between Midas Promotions (company involved in promoting the show in Singapore) and On The Line (Japanese equivalent) that caused the cancellation. Also, Singapore Indoor Stadium can only seat up to "7,306–7,968 during concerts" (
source).