My download directory for Heavy is about the same, but the whole thing is 4.88GB once installed. The files in the download are .bfdca, and the files in the install are .wav. So, I’m assuming .bfdca is a BFD compressed archive file. So it would seem they expand it when doing the install. Why they didn’t just use bfdlac in the first place is beyond me, but anyway, that’s how they did it.
And yeah, other than the lite bonus snare, Heavy is just kicks and toms.
[edit:] And, after running the BFDLAC tool, the final size is only 1.6GB. There’s a conference preso on BFDLAC somewhere on the interwebs, and it explains that something like 33% of all BFD drum data is 0’s. There are other aspects of multi-channel drum data that can be taken advantage of, which is what makes BFDLAC so effective. It’s a much more efficient format, and really, if you still have .wav data, you should be converting it to .bfdlac.