OMG! Overtext! How long have I been sleeping?! OVERTEXT! Also, I'm a DESIGNER now?! Sweet! OVERTEXXXXXXT!
HO HO HO! Give me some money!
I understood this as reducing the number of defending troops that could leave using normal movement in Phase 2, since "pinning" is a concept I am familiar with from other games. It does not affect bolting (retreating) once combat has begun.