What the document says is that the CAA, on the basis of reported encounters, believes the existing separation is insufficient. ICAO has a different separation but when asked had no research or evidence to justify their figure. That ICAO figure is currently the only alternative so the CAA intends to implement the ICAO figure unless somebody can justify a different figure. Rather than fund research and modelling to establish the right figure the CAA is effectively asking those who have most to lose from this change to fund that research for them.