That's also because the way they evaluate risk isnt individualised enough to correctly say that each woman they deem to be high risk is "medically advised" not to have a home birth as it is factually less safe for people like them.
So for example, it might well be factually true for people with many risk factors for pre-eclampsia, but not actually true for women who just have a high BMI. There isn't much good quality research that actually studies how high risk women fare in low risk settings because of the ethics. You can only look at who has given birth and their outcomes and hope you have enough information to control for the many variables.
What they can say is that it is outside of their guidance and then they aren't actually stating that their guidance is based on solid research ie "medically advised". You have to find that out for yourself by reading it.
The law says that care must still be provided even if it is outside of guidance where competence isn't compromised. So at the end of all that, if the woman wants a homebirth, she gets one, and the staff have to plan to minimise risk.