clarify

Marlin/Configuration_adv.h

@@ -991,7 +991,7 @@
     // The probe Z offset (M851 Z) is the height at which the probe triggers.
     // This must be large enough to keep the probe pin off the bed and prevent
     // it from snagging on the bed clips.
-    #define Z_CLEARANCE_BLTOUCH_HS    7 // Extra Z Clearance
+    #define BLTOUCH_HS_EXTRA_CLEARANCE    7 // Extra Z Clearance
   #endif
 
 #endif // BLTOUCH

Marlin/src/feature/bltouch.cpp

@@ -98,10 +98,10 @@ void BLTouch::init(const bool set_voltage/*=false*/) {
     // raising by the offset would give 0 clearance and probe offset is the
     // trigger point, not the contact point. Expect a minimum of 1mm before
     // the probe pin lifts off the surface.
-    #ifdef Z_CLEARANCE_BLTOUCH_HS
+    #ifdef BLTOUCH_HS_EXTRA_CLEARANCE
       // The probe trigger point should be below the nozzle, but there's no guarantee!
-      const float zclear = (Z_CLEARANCE_BLTOUCH_HS) - probe.offset.z;
-      if (zclear > 0) return zclear;
+      const float zclear = (BLTOUCH_HS_EXTRA_CLEARANCE) - probe.offset.z;
+      if (zclear > 0 && zclear < 7) return zclear;
     #endif
 
     // Offset not set or positive (invalid), use BLTOUCH stroke

Marlin/src/inc/SanityCheck.h

@@ -1899,8 +1899,8 @@ static_assert(X_MAX_LENGTH >= X_BED_SIZE, "Movement bounds (X_MIN_POS, X_MAX_POS
       #if BLTOUCH_HS_MODE == 0
         #error "BLTOUCH_HS_MODE must now be defined as true or false, indicating the default state."
       #endif
-      #ifdef Z_CLEARANCE_BLTOUCH_HS
-        static_assert(Z_CLEARANCE_BLTOUCH_HS > 0, "BLTOUCH_HS_MODE requires a positive Z_CLEARANCE_BLTOUCH_HS.");
+      #ifdef BLTOUCH_HS_EXTRA_CLEARANCE
+        static_assert(BLTOUCH_HS_EXTRA_CLEARANCE > 0, "BLTOUCH_HS_MODE requires a positive BLTOUCH_HS_EXTRA_CLEARANCE.");
       #endif
     #endif