Extend error messages for E factors sanity-checks

Marlin/src/inc/SanityCheck.h

@@ -1880,9 +1880,9 @@ constexpr float sanity_arr_1[] = DEFAULT_AXIS_STEPS_PER_UNIT,
 static_assert(COUNT(sanity_arr_1) >= XYZE, "DEFAULT_AXIS_STEPS_PER_UNIT requires 4 (or more) elements.");
 static_assert(COUNT(sanity_arr_2) >= XYZE, "DEFAULT_MAX_FEEDRATE requires 4 (or more) elements.");
 static_assert(COUNT(sanity_arr_3) >= XYZE, "DEFAULT_MAX_ACCELERATION requires 4 (or more) elements.");
-static_assert(COUNT(sanity_arr_1) <= XYZE_N, "DEFAULT_AXIS_STEPS_PER_UNIT has too many elements.");
-static_assert(COUNT(sanity_arr_2) <= XYZE_N, "DEFAULT_MAX_FEEDRATE has too many elements.");
-static_assert(COUNT(sanity_arr_3) <= XYZE_N, "DEFAULT_MAX_ACCELERATION has too many elements.");
+static_assert(COUNT(sanity_arr_1) <= XYZE_N, "DEFAULT_AXIS_STEPS_PER_UNIT has too many elements. (Did you forget to enable DISTINCT_E_FACTORS?)");
+static_assert(COUNT(sanity_arr_2) <= XYZE_N, "DEFAULT_MAX_FEEDRATE has too many elements. (Did you forget to enable DISTINCT_E_FACTORS?)");
+static_assert(COUNT(sanity_arr_3) <= XYZE_N, "DEFAULT_MAX_ACCELERATION has too many elements. (Did you forget to enable DISTINCT_E_FACTORS?)");
 
 #if ENABLED(CNC_COORDINATE_SYSTEMS) && ENABLED(NO_WORKSPACE_OFFSETS)
   #error "CNC_COORDINATE_SYSTEMS is incompatible with NO_WORKSPACE_OFFSETS."