Formal charges can mislead when writing arrow-pushing mechanisms
Arrow pushing is a tool that helps you think about the possible reactions available for a given species or set of reactants: where electrons are likely to move in order to form new bonds and break old ones. But you still have to look at the species that you get after doing the arrow pushing and consider whether they will be favorable or not. Sometimes you can get a reaction between a (formally) negatively charged atom and a positively charged atom - for example between methoxide and tert-butyl cation. Do the arrow pushing and see how that works out.

The reactions you have labeled as incorrect can be seen (via arrow pushing) to produce species that have too many bonds or electrons around a single atom (that was what was meant by the term "hypercoordination" - you could also say hypervalent - for example, having 10 valence electrons around oxygen), whereas the ones labeled as correct lead to stable or at least normally bonded species.