What are -DNRF_PAN_XX used for?

Question

Most of the make files and project files within the nrf5 SDK contain a bunch of defines of the form -DNRF_PAN_XX. A search through the SDK v11.0.0 reveals only a few references to these defines. 
 Are the rest of these defines just artifacts of a previous version of the SDK or do they serve some other purpose? 
 For the ones that are referenced in the SDK should these always be defined or are there cases where it makes sense to not define them? 
 For example the hrs collector example for PCA10040 makefile contains: 
 CFLAGS += -DNRF52_PAN_12
CFLAGS += -DNRF52_PAN_15
CFLAGS += -DNRF52_PAN_58
CFLAGS += -DNRF52_PAN_55
CFLAGS += -DNRF52_PAN_54
CFLAGS += -DNRF52_PAN_31
CFLAGS += -DNRF52_PAN_30
CFLAGS += -DNRF52_PAN_51
CFLAGS += -DNRF52_PAN_36
CFLAGS += -DNRF52_PAN_53
CFLAGS += -DNRF52_PAN_20
CFLAGS += -DNRF52_PAN_64
CFLAGS += -DNRF52_PAN_62
CFLAGS += -DNRF52_PAN_63 
 But none of these even exist in the SDK:
$ grep -rn --include *.h --include *.c --include *.s "NRF52_PAN" *
components/drivers_nrf/hal/nrf_twis.h:36:#ifndef NRF52_PAN_30 /* STOP task is no
t functional in MPW3 (PAN-30) */
components/drivers_nrf/hal/nrf_twis.h:90:#ifdef NRF52_PAN_29
components/drivers_nrf/saadc/nrf_drv_saadc.c:41:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:50:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:72:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:94:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:208:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:278:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:319:#ifndef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:340:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:374:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:389:#ifdef NRF52_PAN_28
components/drivers_nrf/saadc/nrf_drv_saadc.c:412:#ifdef NRF52_PAN_28
components/drivers_nrf/spi_master/nrf_drv_spi.c:60:#ifdef NRF52_PAN_23
components/drivers_nrf/spi_master/nrf_drv_spi.c:436:#ifndef NRF52_PAN_46
components/drivers_nrf/spi_master/nrf_drv_spi.c:474:#ifdef NRF52_PAN_23
components/drivers_nrf/spi_master/nrf_drv_spi.c:491:#ifdef NRF52_PAN_23
components/drivers_nrf/spi_master/nrf_drv_spi.c:562:#ifdef NRF52_PAN_23
components/drivers_nrf/twi_master/nrf_drv_twi.c:579:#ifndef NRF52_PAN_46

Ole Bauck · Accepted Answer

I agree that this is system is not perfect and I have reported this internally for investigation. 
 SDK 11 is designed to support all revisions of nRF52 (rev1 and eng A-C). You can see the actual erratas (PAN) for all revisions here . Only the PAN defines corresponding to erratas on the chip revision should be included in the makefile. 
 As for the PCA10040 hrs collector project this would mean that PAN 30, 63 and 64 should not be defined (even though they are). 
 Some PAN workarounds is also implemented in the startup file (system_nrf52.c) instead of in the SDK.