Chemically, to "isolate" has a bit of a meaning that should be understood. This oil-based method (or similar) does not isolate alkaloids. The alkaloids are concentrated, but not isolated. The tobacco matrix is still quite present though a significant percentage of it is removed in the partitioning.
When talking about the "ethics" of posting a procedure, a good part of the discussion has to involve the presentation of the procedure. The materials used have to be discussed in relation to the science behind their use and also in relation to the possibility of their presence in the end-product and the possible repercussions of their being present in the end-product. So the fate of the oil and sodium carbonate need to be considered, along with the vaping of a significant amount of citric acid. At an acidic final pH, the sodium carbonate is pretty much taken care of. Any that might be present has been quite neutralized. While the mineral oil is basically hydrophobic, there is likely a small solubility of the hydrocarbons in water... could this present a problem? Also, the presumption that vaping matrix components from the tobacco is safer than smoking tobacco is probably valid, it should be made clear that the matrix still may present a degree of hazard that is unknown.
So basically, I'm saying that the procedure needs to discuss anything that is expected to be present in the final product however small the quantity. When the possible hazard of a component of the final product is known, it needs to be discussed specifically. Also, when the possible hazard of a component is unknown, then it would be wisest to say precisely that... without hand-waving or discounting the possible or unanticipated effects. It's a matter of making the fullest disclosure possible such that anyone who might attempt the procedure is forearmed with any specific caution that might be appropriate, as well as the general caution that the end-product may present unknown or unanticipated hazards.
In other words, we do this at our own risk, and the risk is non-zero. If an individual is uncomfortable with the procedure or is not willing to accept full personal responsibility for following the procedure along with full personal responsibility for any side-effect either known, suspected, or unanticipated, then the individual should not attempt the procedure.
That's my view of the ethics.