Apply suggestions from code review

Co-authored-by: Boris Zbarsky <[email protected]>

src/darwin/Framework/CHIP/MTRDevice.mm

@@ -2344,19 +2344,20 @@ - (NSArray *)_getAttributesToReportWithReportedValues:(NSArray<NSDictionary<NSSt
             }
             NSArray * expectedValue = _expectedValueCache[attributePath];
 
-            // Report the attribute if read attribute would get a value that is changing and no expected value exists.
+            // Report the attribute if a read would get a changed value.  This happens
+            // when our cached value changes and no expected value exists.
             if (readCacheValueChanged && !expectedValue) {
                 previousValue = _readCache[attributePath];
                 shouldReportAttribute = YES;
             }
 
-            // Update the readCache with the attribute value.
+            // Now that we have grabbed previousValue, update the readCache with the attribute value.
             _readCache[attributePath] = attributeDataValue;
 
             if (!shouldReportAttribute) {
-
                 // If an expected value exists, the attribute will not be reported at this time.
-                // When the expected value interval expires, the correct value will be reported.
+                // When the expected value interval expires, the correct value will be reported,
+                // if needed.
                 if (expectedValue) {
                     MTR_LOG_INFO("%@ report %@ value filtered - expected value still present", self, attributePath);
                 } else