Magnesium‐based catalysts are becoming popular for hydroelementation reactions specially using p‐block reagents. Based on the seminal report from Schäfer's group (ChemCatChem 2022, 14, e202201007), our study demonstrates that the reaction mechanisms exhibit a far greater degree of complexity than originally presumed. Magnesium has a variety of coordination modes (and access to different hybridizations) which allows this electron‐deficient centre to modulate its catalytic power depending on the σ‐donor properties of the reagent. DFT calculations demonstrate several reaction channels closely operating in these versatile catalysts. In addition, variations in limiting energy barriers resulting from catalyst modifications were examined as a function of the Hammett constant, thereby predicting enhanced efficiency in reaction conversions. Show me how many ligands you accept, and I will tell you how you react: depending on the number of ligands that the ansa‐half‐sandwich magnesium catalyst can bind, our DFT calculations show that the mechanism proceeds differently with competitive reaction channels.