It appears the only reason they are doing gate screening is to prevent people from taking airside purchased beverages on the flight - which is the dumbest waste of resources I have ever seen. My mind is just numb from trying to understand their logic...but because they have none, I will offer some of my own as a counterpoint to their dumbness

To avoid having to deploy resources to gate screen, they could have:

1) banned the sale of all prohibited liquid items through airside vendors until the vendors and airport could...

2) setup fountain dispensers for water, coffee, tea, juice and soda which could be sold in open cups without lids, preventing someone from storing the beverage in their bag...then...

3) have a single screener watch the line to make sure no one boarded with their open beverage cup

Voila...problem solved. No gate screening and no beverage containers on board, but no thirsty customers either.