I'm not sure how the Malaysian asymptomatic stat compares to other countries with Delta, but if it's currently higher, it could be explained by Malaysia being currently swamped with covid. They're not that meticulous at the best of times, but I doubt they're finding the time to reassess after the initial test result. Some of those asymptomatic boxes that were ticked were probably pre-sympomatic when they got their test results and it was never found out or recorded that they later developed symptoms.
