Yes it is trivial for the scope of presidential interpretation to extend over the executive branch. And this excerpt posits nothing about the oversight authority of other branches.

The more interesting phrase is about the AG. While the AG is already constitutionally understood to serve at the president's pleasure, this EO curtails any informal independence that the AG is afforded from past norms.

So I suppose it's declaring that AGs under a Trump administration shall serve as rubber stamps with no independent authority to interpret the law, granted via his claimed constitutional supremacy over the executive branch.

Perhaps it is a edict to AGs who've resisted orders from the President recently, to notice them that job title is the most supreme form of legal analysis in this executive branch. IANAL