NEVER!
As I teach this subject, and safety comes first in my shop, I can say that I am "considered" by most, to be an expert in this subject. This is the only type of stand that I use, and allow in my shop.
Point #1: The stand cannot release if there is a load on it...Period. To release the moveable part you must lift it up, or raise it with the lever.
Point #2: All lifts made in the last 12-15 years uses the same design to support the lift arms and mine are rated for 9,000lbs. I put my life in the hands of this design EVERY day.
This "IS" the Industry standard.
Kary