What is the right way to maintain Time Machine backup history for a HDD with two partitions?
Okay, so it looks like there is no need to worry about losing backup history on the time-capsule as long as the names of the volumes are unchanged.

Since there were no answers here, I just bit the bullet and went ahead with what I had originally intended to do. Fortunately, TC picked up the deltas after I resized and restored the data into Volume_B.

So now you might be wondering why I even bothered to ask in the first place. Well, the reason I was concerned is because the first time around, when I went from a single partition layout (backed up on TC) to a dual partition layout (with the name of the first partition unchanged), TC had somehow decided that it needed to start from a clean slate, and I lost all the history there.