DH during a pass play is previous spot enforcement. But let’s not forgot that a pass play is the interval between the snap and when a legal forward pass is completed, intercepted, or incomplete. DH that happens during any running play (not ‘down,’ but ‘play’) including a running play after a passing play, is true Basic Spot/3&1 enforcement. But, it would be hard to have (or call) DH after a pass is caught or intercepted.
Some may think it can be added to the end of the run following the pass play, but that is not correct. Only personal fouls and unsportsmanlike conduct fouls during a passing play may be added to the end of the last run, and holding fouls are not personal fouls.