HDSDR displays the 7300’s scope on an external monitor (not technically correct, but sufficient). We can get a better resolution and a larger picture of the spectrum scope. It’s possible to see an entire band or more and we can tune the 7300 with our panadapter. Use the mouse, point and click on the desired signal in HDSDR and the radio follows. Any changes made to the VFO, band and mode made by HDSDR are tracked by the 7300 and vice versa. Two videos. First is on the installation of the DXPatrol, Zadig, HDSDR, Omnirig. The second video is just configuring the RTL-SDR dongle in HDSDR. See this article for more information: K0PIR.us
Yeah, great question and I wondered the same when I purchased the splitter. It works fine on 80 meters, I don't know about 160 and I don't know the reasoning behind that particular splitter, but it was recommened and/or used by a couple of other hams. Here's one article: http://www.ab4oj.com/icom/ic7600/ic7600_rtl_sdr.pdf Possibly there is a better alternative.