I don't think that's how the SRE role is described in the book. It shifts the boundaries between sysadmins and developers to give developers much more freedoms

I don't think that's how the SRE role is described in the book. It shifts the boundaries between sysadmins and developers to give developers much more freedoms in deciding the operational parameters of how their softwane is run/released but also gives SREs the ability to push back if they get handed over some piece of software that's not sufficiently following recommended patterns that make actually operating it mostly automated.