This little gem was coined one day when yet another project was doomed to oblivion by the piling on of absolutely critical deliverables after extensive reviews.
"Yeah but"s are actually essential to a successful project. The devil is in the timing. If you're still working around with the direction the New Thing is going to take, you end up with scope-jacking. If you hold it off until you're at the operational planning stage, you're golden. That's when you call it "risk-management".
There are always exceptions - usually when you run into legal issues that prevent directions you can take. Or invisible boundaries when you find out there's a duplicate somewhere.
But as a general rule, do whatever it takes to dodge scope-jacking.