It is possible for affiliate network to be monitoring the contents on the native ads, especially for quality content control. They may want to be monitoring to ensure that the contents really represents their brands and won't damage their reputation.
Also, it may be for monitoring of performance of the niche. Some affiliate networks can even be identifying mistakes made by their users, for them to get themselves corrected.
Also, it may be for monitoring of performance of the niche. Some affiliate networks can even be identifying mistakes made by their users, for them to get themselves corrected.