When a new tag is created on the main site, you get a warning before you can continue - this prevents creation of a tag by mistake. This was implemented as a result of this feature request: Warning for new tags.1
Only today I realized that this warning is only enabled on main site and not on meta.2 I think that it make sense to display the same warning on meta - for the same reasons, mainly to prevent creating a new tag when somebody makes a typo.
Originally I suggested this just as a comment on the older thread, but based on recommendation which I was given there, I am opening a separate feature request for this.
1Thanks to Andrews for the screenshot.
2In fact, I was quite confident that this actually works on both sites - which is why I created a new tag on meta by mistake. My intention was simply to see what exactly the warning says - and, to my surprise, I was allowed to save the edit without being shown any warning at all. (To this I should add that I apologize for bumping an old thread - that wasn't my intention.)