Eeeeyeees....
right.
I think what they are trying to say is that the stall speed increases with the root of the g you are pulling. Ie a 1 g stall in a PA28 is circa 50kts. Pull 4g and in increases by root 4. Inthis case 2. So stall speed in a PA28 under 4 g is 100kts.
At 9 g, it would stall at 150kts etc etc.
Of course an aeroplane could be pulling g in a vertical climb, or any other attitude which is what Collins is trying to say. (I think!)