Just flagging a small typo... the following code excerpt from leave_out_KSS.m (version 3.02) should clarify what is the true default:
%leave_out_level: string variable that takes two values:
%'obs': perform leave-out by leaving a person-year observation out (default)
%'matches': perform leave-out by leaving an entire person-firm match out.
%Default: `matches'.
Just flagging a small typo... the following code excerpt from leave_out_KSS.m (version 3.02) should clarify what is the true default: