I am sure you don’t actually think that holding with small screwdriver is better than 100% PCB fixation?
Why is better? Isn’t that obvious? 
Better control over the work with better centering possibility of emitters(lets say 3030 emitter on 3535 mcpcb), less time on hotplate, more accurate dab or tap move(if someone wants to do that).
Didn’t you had reflow problems recently? Try to eliminate that by fixation method.