Snapchat has been more aggressive at push notifications (such as @xxx friend posted a new story!) to move more MAUs / WAUs into DAUs category. These strategies

Snapchat has been more aggressive at push notifications (such as @xxx friend posted a new story!) to move more MAUs / WAUs into DAUs category. These strategies have been employed by other competitors as aggressive as well though. So it is probably still comparable. I would say Snapchat's metrics are more "authentic" a few years ago, but now it is more "comparable".