When I worked at a certain three-letter-agency, much of the annual legal training amounted to "Here's our incredibly tortuous interpretation of every relevant term in the letter of the law. Don't like it? There's the door."
It would frankly be insane if your three-letter agency _didn't_ work this way. Everyone needs to understand what the interpretation of the law is, what the legal guardrails are. If you disagree with this, the answer is not just do what you want with FISA.
That is, the interpretation was meant to justify what people might be tempted to do.
"Oh... I was going for promo."
Self selection would be one example. To be fair, when I once had a beer with someone who worked in that area before coming to academia she basically said you could work out how many intelligence officers a country had, and realise that given the amount of time effort and money it takes to properly surveil someone they were limited to a small multiple of that number of people to spy on "properly". I felt reassured by that. I can also see it being a justification for RoboCop.