Why put a invisble wall in Divintiy's reach?

[AzuraBlackcoin.1809]

When Wintersday came around, there became an invisible wall around the Central Plaza.Which makes so that I can no longer get reall high up and fly around Divintiy's Reach with my griffon.This seems like a very strange change and unesscary, I want to fly around in Dinvity and enjoy the scenery from up top.Here for example a screenshot I took before the change:https://imgur.com/a/REqRA