Does Anyone Know When (and Why) This Change in PGP Happened?

I have used Pretty Good Privacy (PGP) for a very long time now. One thing I particularly liked about it is that the encryption not only scrambled the content of email, it obscured its length. I can recall receiving a long, encrypted message, and upon decrypting, a very short message was revealed. Similarly, long unencrypted messages were not noticeably, nor predictably longer than short ones when encrypted.

But that has changed; nowadays it’s fairly easy to gauge the length of an email by its encrypted length. At least, it is for me; I’m currently using KGpg, with my PGP keys that were generated a couple of years ago (don’t recall what version of PGP that was). What changed in encryption tech to cause this loss of file-length obscuring?