Well, that’s a different question, but I must confess I dont know what you mean by ‘tracing along’ 
I am not sure that sounds as an explanation to me… there appear EXTRA faces due to small size of the model? there appear extra face when you draw an edge in one direction, and does not in the opposite? doesnt sound related to small size of the model to me… if there were no face created then it would make sense.
UPD
but you are right, it disappear after scaling. To me it seems to be a SketchUp bug.
you need to purge after deleting? sorry for being a newbie, but how do you do it? =)
Regards,