I’d argue there could be a reason to use ‘least’ over ‘fewer’: they may be intending to emphasize the lesser impact of some changes over others, and not simply be referring to the number of changes that were made. It is possible to have a larger number of changes to a route and still end up with a lower impact to riders than another route than technically has fewer changes.

Completely agree on the language crusade, we have these fads and memes all the time where some people decide there’s only one way and try to forcefully correct others without understanding the history of these words. I have even been guilty of doing this on occasion in the past but have learned over time that language policing is almost never correct. It is not wrong to say “myriad of”. The word “literally” has been used for figurative emphasis for hundreds of years by some of our greatest writers. Responding to a ‘how are you?’ with “I’m good” or “I’m doing good” rather than “well” is not incorrect and does not communicate that you’re an angel. People, all of us I think, are just prone to getting notions about what’s right and wanting to demonstrate our found knowledge, but it’s easy to not be aware of alternatives.