Failing to register your child's birth because of your ideology is dodgy as fuck, whether it's because of your strange ideas about 'sovereignty' and the relevance of obscure maritime law, or because of your strange ideas about sex, gender and motherhood.
https://www.whatdotheyknow.com/request/if_a_child_has_not_been_register
www.theguardian.com/uk-news/2019/jun/23/man-refused-to-register-sons-birth-high-court
Children who are not registered are at risk because legally they don't exist so they don't show up on anyone's radar.
Freddy's two will be fine because she loves the limelight so everyone knows of these two children's existence but what kind of example has she set? Are there other mothers who have failed to register their children because they believe themselves to be fathers? Maybe really vulnerable messed up young women who might not even have publicly come out as 'trans'?
The number of unregistered births in the UK is a known unknown.