Well... you guys are mostly speaking from experience with acquired skills. I can see some advantages to breadknifing for a newbie.

Yes, it's probably going to remove way more material than necessary.
Yes, it's probably going to require orders of magnitude more work.

But... consider a newbie sitting down with his new stones and newly acquired (old) razor in questionable condition.

You don't have the skill to know exactly what's wrong with it.
You don't have the skill to know the extent of the existing damage (or kind of damage).
You don't know what was done to maintain it or repare it previously or if it was done correctly.
You probably aren't using a microscope and may not know what to look for if you are using one.
Could be an uneven edge, chipped edge, double bevel, multiple bevels at different places on the edge, completely too steep of a bevel from someone sharpening it at a 20* angle like a knife, etc.

So you bread knife it. You KNOW that you're starting from scratch. That's a big plus.
If you follow the procedures described everywhere here you know what the result should be and that it's going to be somewhere in the ballpark of what you expect. Sure, you're probably going to quickly find that it's going to take 10 times as much work as you expected but at least you have some idea of where you're at.

Let's take the example where the previous ebay seller, who knew nothing about razors, tried sharpening it up like a knife on some really coarse stone or sand paper holding it at a 20* angle. You're going to get this thing and it might feel sort of like it has an edge and you're going to start honing on your 4K Norton. You're going to see shiney effects on the edge and think you're getting somewhere when you're just working (very slowly) on the second bevel. This could be very perplexing for a newbie right?

Besides, don't you think everybody should hone a razor from scratch just ONCE to get an understanding? Once you do that I'd expect you'd have made a quantum leap in being able to evaluate the next one before you start on it.