Good question … and one that ought to be discussed setting all agendas and alleged agendas aside. [other than pursuit of truth and justice, obviously - those agendas should always be front and center.]
One short critical answer to the “will this cancel itself out” question is: “well, then, why hasn’t it?” Ocean levels and CO2 levels are still rising and have been for some time. Those are the measured facts on the ground.
Everyone agrees that climate change is not some simple thing to model - which causes climate scientists to reach their conclusions with conservative caution (and so far it has generally proved very conservative compared to what’s actually happening) and gives an agenda-driven public plenty of uncertainty to try to pin various (non-conservative) hopes in if they don’t like climate change implications.
I don’t think anybody disputes that more CO2 generally promotes more photosynthesis and greenery. And as such that could be a mitigating factor as far as atmospheric carbon removal goes, but an insufficient one, apparently. For one thing, I would want to hear climate scientists weigh in (or research where they have weighed in) on what kind of plant matter is being added. Clearing of tropical jungles and such removes lots of greenery (especially trees) which is not in our favor - is the increased plant growth a sufficient offset for that? And is it the same kind of growth? I.e. trees vs. grasses. Is the latter only a more temporary kind of carbon sequestering that is “burned off”, seasonally returning more of its carbon to the atmosphere than trees would? Those are the sorts of questions that might affect whether this would end up being mitigation at all. And as such, it would join the ranks of a myriad of factors that models have been obliged to try to account for - no doubt a blend of endangering factors (positive feedback variables) as well as moderating (mitigating) factors as this discussed one might be. But all factors considered, in the end we are obliged to acknowledge the emerging data as it is revealed.
So I’m glad you add your caveat that you see that the concern remains and that these questions can be asked and answered legitimately - as we should. Hopefully others here can volunteer more data than I have time to round up today to either verify or correct some of what I’ve written here already just off the top of my head.
[edited to remove some of my own editorializing…]