The issue with these sorts of undiscussed mechanical edits is their potential for unintended side effects. 
This wiki page describes it very well
https://wiki.openstreetmap.org/wiki/What%27s_the_problem_with_mechanical_edits%3F

These edits could be totally fine, but it could also turn out that there is some kind of issue with them that the editor didnt foresee. and if that happens, then it would be all over the map, things would need to be potentially reverted and suddenly its a way bigger issue. 

This is why mechanical edits are best discussed beforehand. To make sure everyone is on board and people can discuss and bring up potential issues and pitfalls. 

