http://en.wikipedia.org/wiki/Beta_reader
Also, I've been to college too. As an English major. Moreover, I'm currently in graduate school for publishing, so I also know what different positions do in relation to a manuscript. (Even the ones that are technically not professional, such as a beta reader.) I can safely say that, no, beta readers don't just check grammar and spelling. It's likely that your friend's friend was thinking of a copy-editor, which is both professional and essentially someone who checks those kinds of details but shies away from modifying the actual content of a piece.
Besides, even if that's all they did, why would the Beta Thread have betas that are specifically geared towards checking plot and characterization? Also, why would you ask for a character beta reader if you think one wouldn't check anything but your spelling and grammar? Sincerely curious here, just to get a good idea of what you were asking the people on the Beta Thread to do for you.
Lastly, if I may ask, where exactly did this point even come from? Last I checked, in my first VM to you this month, I was pointing out that beta readers might not be comfortable working with you because you seem to be hostile and resistant to listen to any of the people who try to give you advice (given what you said in the A/N of your fic). I never said anything about what a beta reader does.