The premise is "regenerative grazing can't be made climate friendly".
Any argument not in support of that premise is a non sequiter. Scenario B being climate friendly has no bearing on scenario A being climate friendly. This is a basic rhetorical mistake the author is making and it's sloppy.
A and B are cars. The premise that I'm making is that car A won't get you to Chicago.
If I make the argument that car B is sufficient to get you to Chicago, this has no bearing on my premise.
Vegetarian diets being "better" has no bearing on the sustainability of beef production. A diet of only dark chocolate would be "worse" for the climate than one which consumes beef. It also has no bearing on the sustainability of beef production.