This study was done by pharmacists who rely on clinical documentation by others to assess complications.  Documentation is not always present, thorough or accurate.  Personal experience with usual assessment techniques and ultrasound assessment shows non-compressible veins and induration with 3% saline PIV infusions.  The only way to prove there is no thrombophlebiits with PIV hypertonic saline is to do a study that shows the before and after ultrasound assessment of the peripheral vein and should include the vein location and size (before and after the infusion),  the concentration and rate of saline.  Plenty of nurses continue to infuse fluids through an IV with phlebitis and infiltration without removing it or accurate documentation.  I have seen this throughout my 30 yr career.  Nearly 100% of PIV infusion of hypertonic saline I've seen resulted in phlebitis, thrombophlebitis and non-compressible veins via ultrasound assessment.