Elizabeth, since my posting, wikitree has instituted a new policy that people wanting to edit profiles of people born before 1700 need first to successfully answer the questions on the Pre-1700 quiz.
But no, one does not have to be on the Trusted List to edit profiles older than 200 years. So whoever told you that is incorrect. If the profile has a Project Protected label on it, it is requested to discuss major changes before making them. That would include adding children or spouses.
Now, if you want to change the Last Name at Birth (aka LNAB), you need to be a Profile Manager of said profile-- of whatever age-- AND if said profile is Project Protected, a Leader will have to remove the protection first. But chances are, if a profile is protected, it's LNAB should not be changed. In any case, discuss changes before making them on protected profiles.
All this may seem confusing-- it took me awhile to fully understand it. The intent is to keep profiles open while protecting the privacy of the living as well as protecting the significant research that has gone into the oldest profiles.