Sorry, should have explained further. I was mentioning it in the specific context of using it as a leveraging technique (rather than simply getting the seatback out of the way). It's something that makes it physically possible to overtighten a seatbelt, which you can't do with your arms alone.
Sometimes you need to do the seatback trick, sometimes it makes things easier. I've done it with Frontier LBP in the front of my Safari. But I said "generally" meaning it's not something most people should need to do to get an acceptable install with most vehicles and most seats. And it should be done carefully, without using the top of the seat as a lever, with the end result being a normal install. Not with the goal of getting it beyond tight.