Yes, index is unused. That's ok.

tannewt · tannewt · commit 5e4cb4f1e244 · 2021-12-15T13:46:31.000-08:00
diff --git a/ports/broadcom/common-hal/neopixel_write/__init__.c b/ports/broadcom/common-hal/neopixel_write/__init__.c
@@ -101,6 +101,8 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t *digitalinout,
     if (index == 1) {
         pwm = PWM1;
     }
+    #else
+    (void)index;
     #endif
 
     pwm->RNG1 = 24;

Original file line number	Diff line number	Diff line change
`@@ -101,6 +101,8 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t *digitalinout,`
`101`	`101`	`if (index == 1) {`
`102`	`102`	`pwm = PWM1;`
`103`	`103`	`}`
	`104`	`+ #else`
	`105`	`+ (void)index;`
`104`	`106`	`#endif`
`105`	`107`
`106`	`108`	`pwm->RNG1 = 24;`