Yes but... um...;p
I've found a lot of times when yes but is used I am fully in agreement with the statement as stated. Yet when more variables are added, the situation is no longer true. A narrow point of view can be fully accurate, while a larger perspective makes things no longer work the same.
For example the general held belief of 1+1=2, which is true in a majority of real world situations. BUT in a programming language that uses floating point numbers where 1 cannot be represented precisely might represent 1 as 0.9999. Then 1+1 becomes 1.9998, which represented as an integer (no fractional value), typically truncates the fraction so 1+1=1.
So is yes but a hidden disagreement with the original statement or a full agreement of the original statement as stated but with the intent to show the statement is too narrow of the perspective? Much like this reply...