While Apple will not pull existing apps from the App Store for not adhering to this guideline, it will prevent developers from updating their apps until they get around to complying with this change.
While Apple has always kept the privacy of its users as one of its primary objects, it has come down heavily in recent times on offending apps and become more strict in this regard. The company even told Facebook to remove its popular VPN app from the App Store since it was not adhering to the App Store’s guidelines. In this day and age where every company just wants to get their hands on as much user data as possible, it is good to see a company like Apple ensure that the data and privacy of its users are not compromised in any way by having a tight control on its own platform and ecosystem of apps.
Apple has also updated its App Store guidelines this year to prevent apps from collecting user data for marketing purposes.