📝 Fix X2_MAX_POS comment (#23873)

Marlin/Configuration_adv.h

  */
 //#define DUAL_X_CARRIAGE
 #if ENABLED(DUAL_X_CARRIAGE)
-  #define X1_MIN_POS X_MIN_POS   // Set to X_MIN_POS
-  #define X1_MAX_POS X_BED_SIZE  // Set a maximum so the first X-carriage can't hit the parked second X-carriage
-  #define X2_MIN_POS    80       // Set a minimum to ensure the  second X-carriage can't hit the parked first X-carriage
-  #define X2_MAX_POS   353       // Set this to the distance between toolheads when both heads are homed
-  #define X2_HOME_DIR    1       // Set to 1. The second X-carriage always homes to the maximum endstop position
-  #define X2_HOME_POS X2_MAX_POS // Default X2 home position. Set to X2_MAX_POS.
-                      // However: In this mode the HOTEND_OFFSET_X value for the second extruder provides a software
-                      // override for X2_HOME_POS. This also allow recalibration of the distance between the two endstops
-                      // without modifying the firmware (through the "M218 T1 X???" command).
-                      // Remember: you should set the second extruder x-offset to 0 in your slicer.
+  #define X1_MIN_POS X_MIN_POS    // Set to X_MIN_POS
+  #define X1_MAX_POS X_BED_SIZE   // A max coordinate so the X1 carriage can't hit the parked X2 carriage
+  #define X2_MIN_POS    80        // A min coordinate so the X2 carriage can't hit the parked X1 carriage
+  #define X2_MAX_POS   353        // The max position of the X2 carriage, typically also the home position
+  #define X2_HOME_DIR    1        // Set to 1. The X2 carriage always homes to the max endstop position
+  #define X2_HOME_POS X2_MAX_POS  // Default X2 home position. Set to X2_MAX_POS.
+                                  // NOTE: For Dual X Carriage use M218 T1 Xn to override the X2_HOME_POS.
+                                  // This allows recalibration of endstops distance without a rebuild.
+                                  // Remember to set the second extruder's X-offset to 0 in your slicer.
 
   // This is the default power-up mode which can be changed later using M605 S<mode>.
   #define DEFAULT_DUAL_X_CARRIAGE_MODE DXC_AUTO_PARK_MODE

Marlin/src/module/motion.cpp

     );
     // Transpose from [XYZ][HOTENDS] to [HOTENDS][XYZ]
     HOTEND_LOOP() LOOP_ABC(a) hotend_offset[e][a] = tmp[a][e];
-    #if ENABLED(DUAL_X_CARRIAGE)
-      hotend_offset[1].x = _MAX(X2_HOME_POS, X2_MAX_POS);
-    #endif
+    TERN_(DUAL_X_CARRIAGE, hotend_offset[1].x = _MAX(X2_HOME_POS, X2_MAX_POS));
   }
 #endif
 
   bool idex_mirrored_mode                = false;                         // Used in mode 3
 
   float x_home_pos(const uint8_t extruder) {
-    if (extruder == 0)
-      return X_HOME_POS;
-    else
-      /**
-       * In dual carriage mode the extruder offset provides an override of the
-       * second X-carriage position when homed - otherwise X2_HOME_POS is used.
-       * This allows soft recalibration of the second extruder home position
-       * without firmware reflash (through the M218 command).
-       */
-      return hotend_offset[1].x > 0 ? hotend_offset[1].x : X2_HOME_POS;
+    if (extruder == 0) return X_HOME_POS;
+
+    /**
+     * In dual carriage mode the extruder offset provides an override of the
+     * second X-carriage position when homed - otherwise X2_HOME_POS is used.
+     * This allows soft recalibration of the second extruder home position
+     * (with M218 T1 Xn) without firmware reflash.
+     */
+    return hotend_offset[1].x > 0 ? hotend_offset[1].x : X2_HOME_POS;
   }
 
   void idex_set_mirrored_mode(const bool mirr) {