The -6 pump inlet fitting is steel, and the elastomeric line feeding it should have steel ends and nuts. I suspect that use of standard AN torque tables may contribute to loosening. Consider, for example, the Aeroquip page published by Vans:
https://www.vansaircraft.com/pdf/Torque_Spec_Aluminum_Fittings.pdf
The torque call-out for a -6 is 130 to 180 inch pounds, or 10.8 to 15 ft-lbs. However, those values are for aluminum fittings, not steel. The page tells you to refer to Bulletin JA14A (another Aeroquip publication) for steel fittings, but JA14A only describes the flats method.
There are lots of guides for tightening hydraulic fittings in industry, and the SAE straight thread/o-ring to male flare pump fittings most of us are using are straight from the hydraulic parts bin. Dig around in the industry charts, and you'll see oiled -6 JIC 37 degree flare torque around 16 to 20 ft-lbs, and dry fittings at 20 to 22.
There is another factor which may play into a few loose pump feed hoses. A builder may select a straight, 45 degree, or 90 degree inlet fitting. If he selects a straight fitting, a 90 degree steel tube hose end becomes the most likely choice. The potential problem is that a hose approaching from a fixed point on the firewall can then serve as a lever when the engine moves on its mounts. It is 90 degrees to the fitting axis, in the plane of rotation necessary to loosen the B-nut. Me? I use a 90 pump inlet fitting and a straight hose end. I think the fitting's o-ring seal more resistant to leakage if the clamp nut is loosened, and even if backed off, the fitting itself can't rotate out of the pump.
I previously said the fittings should be steel. As far as I'm concerned,
all the firewall forward fuel and oil fittings should be steel. They're fireproof, and far more fatigue resistant, goods reason to use them. However, they're also friendly to the goodntight method Tom mentioned previously. It was a forum contribution by Walt Aronow who convinced me to add a habit to my maintenance; I grab an open end and tug every fuel fitting every time the cowl comes off. No torque wrench, no counting flats, just a firm pull. I know, failing to use a torque wrench isn't kosher, and surly I shall suffer God's own wrath as a result...but I'm sure the fittings are tight.