I've worked in both the private and the public sector and also as a a consultant in both environments. Whether the environment is a sweetheart deal, depends on the employee's risk tolerance and their need for stable employment versus opportunity for advancement. Because an employee values stable employment has little to do with their job performance.In other words, the conclusion is based on the assumption, unproven, that the high skills level of government workers is not needed. The fact that the study comes through the Heritage Foundation, a conservative think tank further discredits the claim.
Federal and state gov't jobs have a less than 6% annual turnover, and it has been this way for many years.
If they were paid so much less than the private sector - they would leave, except they don't, because they know they have a sweetheart deal. Private sector turnover is far higher, and it is because of the lousier work conditions, lower pay, etc.
The facts are on the ground, and the public union employee defenders/sycophants can try and spin this BS any which way they want - the truth is there for all to see.