Separation Assurance is not possible or practised in Approach or Departures environment so the scenario of one departing SY/PH is not applicable. As much as I think sep ass is bs, it is mainly applied in the enroute environment.
The runway standard applied to a landing behind a preceding departing aircraft is that you do not permit the landing aircraft to cross the runway threshold until the preceding aircraft is airborne and:
a. has commenced a turn; or
b. is beyond the point on the runway at which the landing aircraft
could be expected to complete its landing roll; and
c. there is sufficient distance to enable the landing aircraft to
manoeuvre safely in the event of a missed approach.
Maybe in this instance the Virgin pilot made the decision to go round catching the ADC by surprise?