How do we ensure that the initial "land-grab" of tags goes smoothly without introducing redundant tags?
I believe that registering such tags as synonyms is a good thing that benefits everyone. Different people have different ideas of how the tag might be called and thus will initially just use what comes to their mind.
With registered synonyms, those tags will automatically get promoted to the canonical rendition, thus in effect reducing unwanted redundancy. That being automatic means they aren't forced to consult a list of canonical (master) tags and their synonyms first before being able to use them. They can simply tag away and the machine (site) does the labor of canonicalizing the tags for them.
Also, someone searching for a synonym, unaware of the canonical (master) tag, will then automatically find the questions that have the master tag.