I take your point - it depends on the situation. But I'd don't think you'll ever find me saying that in general coasting engine-off in car that normally has power steering is
safe.
(PS. the brakes aren't the issue - there's enough vacuum reserve with the engine off for at least one full assisted stop.)
About drafting: it's not the vehicle in front that I'd be worried about in the event of an unexpected slowdown or stop. In fact I'm quite sure you're driving in a state of let's say heightened awareness. It's the vehicles behind you that pose the biggest threat.