Hmm, I think there is some confusion here. Slicing from the end is perpendicular to the grain. Slicing from the corner (like you would with a tri-tip) would be diagonal to the grain.
Separate the point from the flat, as both have their grain going in opposite directions. Slice directly against the grain without any angles.
I see what you're saying, when you slice on an angle you're hitting the grain at a perfect right angle. I don't think this is necessary, although I can't say I've tried.
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