It's the imagepack version, which is ~10 times the filesize because it contains a whole slew of in-line images for certain scenes, as well as having much larger character art/busts when you click the buttons at the top left corner to expand them.
If you have it, you don't need the smaller .swf version (contains the same content plus extra images), but it is much chunkier and if you're trying to load it on a mobile flashplayer for example, it may chug very slowly.
At first glance, it seems to be just another iterative update to the previous imagepack version, couple more images added to the pile (0.8.130 is 575mb, compared to 0.8.128 being 574mb).
The use of "THICC" may just be for comedic effect (poking fun at the filesize, though it has been roughly this large for a while now). Or perhaps the specific new images added were for thicc characters, I haven't checked the new ones.
But it's mostly the same images as previous versions so it's not like a total art overhaul or anything like that.