A blocking indicator prevents the ordinary referent from being the intended one in a particular figurative occurrence. A non-blocking indicator may guide the listener to an implication without excluding the surface sense.
In “I saw a lion shooting,” “shooting” directs us toward a human agent. In “long sword strap” used to suggest tall stature, the reasoning differs: a genuinely long strap remains conceivable.
What matters is not merely whether an indicator exists, but what that indicator does: exclude the primary meaning or permit it alongside a further implication.