It looks to me like he's either changed his mind, or is playing fast and lose with what the word "sex" means.
I'm guessing that Starmer believes people can change sex. So single sex spaces and attraction are not affected because you can identify as whatever sex you want.
www.dailymail.co.uk/news/article-11651245/Keir-Starmer-sides-Nicola-Sturgeon-Scottish-gender-law.html