Add a piece of angle to the bottom end if you are worried at it. A 2x2x1/8 about 8" long piece of angle welded on pulls harder then a piece of rebar.

I understand your concern. But if you concentrate on driving that terminal end in , they seldom dislodge. Typically the Beaver drives them deeper as they struggle. Most of the times I have had issues is with rip rap or rocky situations.
When current exists like during Spring run-off point the anchor down stream.

I deal with the exact kind of bottoms you describe. I favor the 1/2 rerod for holding in that situation over the more flexible alternatives.