I've only seen that theorem used under the assumption that $L_FL_E=0$, so I'm not overly worried but let's see if I can cook up either a proof of the stronger claim or a counterexample :)
I wonder whether the 1-truncatedness of the map $\operatorname{BGL}_1(\mathbb S)\to\prod_p\operatorname{BGL}_1(\mathbb S_p^\wedge)$ follows from these fracture squares.
It seems related to the functoriality of the Sullivan's arithmetic square applied to the subcategory of $X\simeq\mathbb S$.