Gah! Data sheets.

I was looking at building a remote controlled volume control for use at home. Probably won't happen, but I came across this device:
https://www.nisshinbo-microdevices.co.jp/en/pdf/datasheet/NJU72344_E.pdf
Page 7 gives the serial protocol. It mentions S and P bits, but as far as I can see they're nowhere else defined.
Further down the page, it describes an auto-increment function. That is the only mention.
At the bottom of the page it talks about the consequence of an audio signal being inputted (sic) before (during?) power on. Hard to know exactly what the intent is, but based on that, I'd be concerned that the device might latch up, or otherwise misbehave, if there's any input before power on. Be great to build a bunch of boards with this and then discover that some proportion are flaky.
How many designers would conclude that this could be more trouble than it's worth, and find something else?
Sylvia.