Question about increasing the linearity of PFD

In Thomas Lee's book, it said, in order to increase the linearity of PFD, sometimes DC offset is added intentionally. This remedy will introduce static phase error, so it is not proper for the applications which require small error. Anyone knows why?

Static phase error is still locked in freuqency, so i believe it is a good way to do it.

i think it means that the Output will not be in phase with the input (i.e. there is a constant phase error) which is suitable for applications like ZDB

safwatonline, would you please explain what is ZDB?

Zero-Delay-Buffer: well, the name explains itself