“Independent” agencies have always been a distinction within the executive branch, not a distinction from thr executive branch, so while arguably true on its face, your statement is also a strawman.
> “Independent” agencies have always been a distinction within the executive branch
The common use of the expression "fourth branch of government" to describe independent agencies belies your assertion here.
> have always been a distinction within the executive branch
“Always” is doing heavy lifting here. Independent agencies were a paradigm shift under FDR. We’re presumably seeing a shift away from that paradigm.