I'd be hesitant to take what your family member said as doctrine, or that it's any different than any other Cabinet or other part of the Executive Branch.
It's important to make the distinction that while the President doesn't know all of the things that the Intelligence Community is doing at any one time, there isn't anything that he can't know. It's no different in any other part of the cabinet - the Cabinet members and senior executive service all ultimately decide what hits the desk of the President, so in that sense there is an entire staff "controlling what the president knows." Same as any large organization.
The DNI, DIRNSA, DCI, JS/J2 and all service 2's all work for the President, and they collectively are the ones who "know all the things" - so you can bet if he needs to know something, one of those people will give it to him.
A former civilian nuclear war planner, I think while working for RAND, learned about the existence of the US military plan for the actions involving nuclear weapons: the plan specified the amount of nuclear response to any conflict, which is fundamental for anybody who has the power to resolve conflicts (a president) to know.
But the civilians weren't allowed to know that the plan even existed: the planner also learned that no other civilian, including the people around the president and the president himself, even knew that the said plan existed: it's very existence was being actively hidden from "civilians." They also had a method for delivering them "something else" if the "civilians" asked "about" that topic.
The military managed for years to operate (to be trigger ready) on the plans they kept completely hidden from anybody, including the president.
The president or anybody around him had explicitly no chance to get that by their own initiative.
Everything nicely documented in the book "The Doomsday Machine: Confessions of a Nuclear War Planner." Read it and weep.
It's important to make the distinction that while the President doesn't know all of the things that the Intelligence Community is doing at any one time, there isn't anything that he can't know. It's no different in any other part of the cabinet - the Cabinet members and senior executive service all ultimately decide what hits the desk of the President, so in that sense there is an entire staff "controlling what the president knows." Same as any large organization.
The DNI, DIRNSA, DCI, JS/J2 and all service 2's all work for the President, and they collectively are the ones who "know all the things" - so you can bet if he needs to know something, one of those people will give it to him.