InUCF with TIG constraints, the timing report (.twx) shows the associated path under TIG analysis. But, in the PlanAhead tool, after creating a project importing P&R results, the Timing Results list this path under Unconstrained Paths. Yet, path property displays TIG as applied constraint.
These paths should not be considered "unconstrained", as they are actually covered by TIG constraint.
In ISE Design Suite 13.2, the PlanAhead tool has been enhanced to make the report more clear for TIG constraint.