I think the phrase "pulling a trait" is used to clarify, that you need as recessive a trait as you can get to heighten the chances to actually SEE the hidden trait of the kitty you try to decipher. Trying to "pull" a hidden eye with a very dominant eye partner won't really do as the hidden would just end up being hidden again.
Just my 2 cents and trying to break a lance for those using the phrase.
