Safety stops are best done when you’re completely horizontal in the water so that your entire body is at the same depth and decompressing at the same rate. And if you’re holding onto a line in a current then there’s more space for other divers to be at the correct depth.
A former SCUBA Dive Instructor, I learnt to dive in the UK and taught both here and abroad. After that I spent a lot of time working with dive equipment from all of the major brands. From the Arctic Circle to the Tropics and Apnea to Closed Circuit, most of my professional life has been spent in the scuba diving industry.