Regular season starts or did it?

The Oakland Athletics and Seattle Mariners flew to Japan for a series of exhibition games with two Nippon League teams. Then the Athletics and the Mariners played two games that were reported to be the start of the MLB regular season. Yet after they come back the Athletics and Mariners both have additional games scheduled to be played in the Cactus League. How can this be? What sport has ever started regular season play and then returned to play more pre-season games? From their performances against the Yomiuri Giants and the Hanshin Tigers the MLB was not represented well. I'm inclined to think that the two games between the Athletics and Mariners were nothing more than Cactus League games played on the road in Tokyo.