Of course not. Although if you calculate all the probable outcomes of a walk and a single, it's closer than most people think...
I didn't say OBP is the only thing that matters. I said it's the most important determinate of run scoring, at least on a team-wide basis. A guy with a .290-.300 OBP who can hit 35 or 40 homers is moderately valuable, but only if there are guys in front of him who can get on base for him to drive in. A team of that guy would be a fairly average offense in spite of leading the league in HRs by a mile and slugging by a healthy margin as well. Alfonso Soriano has quietly slugged .489 over the last 3 years - one of the better slugging percentages in the NL over that time (17th) - but nobody wants him at even a reduced pricetag. The Cubs can't move him. You don't think his .312 OBP has something to do with it? Here are a few NL players with lower SLG numbers over the past 3 years: Ryan Zimmerman, David Wright, Andrew McCutcheon, Pablo Sandoval, Hunter Pence, Adam LaRoche, and Jason Heyward. You think those guys aren't valued head and shoulders above Soriano? Of course they are. And their OBPs all exceed his; other than Sandoval, they really all blow him away.
Please note that I never said I would throw SLG away. But OBP is vastly more important. That's all.