If you install it under the tank before the fuel pump there's no pressure on it. Or anyway, almost none—just whatever is generated by having gas in the tank.
It's the same thing for a fuel return line from the fuel injection rail: it's open at the tank end so pressure is de minimis.
I was thinking the same thing, but did not post for a couple of reasons:
I've been uncomfortable with this device from the first post. It's really just a quick release valve, and relies on o-rings and a check ball (one would hope made of stainless steel, but who knows) to shut off the flow when disconnected. I'd be really concerned about the ethanol in fuel degrading these o-rings to the point of leaking, and also about the ethanol compromising the phenolic the body is made of.
Secondly, what is the flow rating of this device? I'd suspect it's greatly undersized to support 150 hp (+/-). Judging from the size of the housing, I can't imagine it flows anywhere near the capacity of an uninterrupted hose. I'd want to know the flow rating before I put a giant restriction in the fuel line.
Maybe I just worry a lot, and maybe there's no issue at all with either concern, but I wouldn't want to be the guinea pig.
FWIW, these are available at CB Performance for less than $20, and they work.