I see that the appendix does not alter the preamble to Part 2, so IRPCAS still apply between boats racing and those not. With the proliferation (sometimes mandatory) of AIS on offshore races, it's now far easier to know whether other boats encountered offshore at night are racing or not, and this appendix does address one of the main difficulties of IRPCAS while racing - marks. (e.g. an inside & windward boat not having any right to mark room). 

WS may like to think about amending the wording of " a replacement for the IRPCAS in overnight " to " e a replacement for the IRPCAS between boats racing in overnight" and from " apply the IRPCAS, for example, between sunset and sunrise." to " apply the IRPCAS between boats racing, for example, between sunset and sunrise."

The biggest issue with IRPCAS at night is that there is a stand on boat, not a right of way boat.  The stand on boat is required to do just that (until such time as it is required to take avoiding action), so the stand on boat cannot change course eg to round a mark. I've had that issue with an evening start (last light) and a mark rounding shortly after (in the dark) where the fleet was still bunched and, according to IRPCAS, we were not allowed to round the mark because we were the stand on vessel.  There was a lot of shouting and alarm, but we all managed to avoid each other.  Appendix RV attempts to address this issue - but it fails.  

Since, in the dark, you can't know if another vessel on a collision course is racing or not, IRPCAS is the only safe option.  And race committees should never set a course with mark rounding in the dark when the fleet is likely to be bunched.  
See also: https://www.rya.org.uk/racing/running-racing/guidance-good-practice/racing-under-the-irpcas 

PS in response to Ed's comment - AIS doesn't tell you if a boat is racing or not.