Right. The slim can bit stream those codecs as well, since it has a more up-to-date HDMI transceiver chip.
If your receiver can handle 7.1 LPCM, there's little benefit to bit streaming, though. Your PS3 will use the SPUs to decode all of the high def codecs on its own just fine. If you have your receiver do the decode, you might save some SPU cycles on the PS3, but the slim is energy efficient enough for that not to be such an issue anymore.
Also, if you bit stream, BD-Java on the disc might have difficulty mixing in player-generated audio effects into the movie audio. When the PS3 sends LPCM to the receiver, it's easy for sound effects from the disc's interactivity to be properly layered in.
Now, when the PS3 first came out, Sony hadn't implemented some of the codecs (DTS-MA) in the firmware, and at that time, those codecs simply weren't available on the PS3, and bit streaming for those codecs would have been a significant benefit.
These days, not so much.