Pre Covid, the established pattern on the Direct itself was 4tph from Waterloo on the quarter hours - the half-hourly semifasts ran through to Harbour, the hourly through stopper terminated at Portsmouth and Southsea, and the fourth hourly train was a stopper terminating at Haslemere.
Post Covid the timetable has been something of a mess, with one of the semifasts being removed but other services not re-timed, giving a mix of quarter hour and half hour gaps in departures. Initially that meant only one tph to Harbour as the stopper still terminated at PMS. There were other weird ideas like the Haslemere terminators running fast with stops only at Woking, Guildford and Godalming, making them rather pointless and meaning that the through Pompey stopper had to pick up minor stations like Milford and Witley, normally served only by Haslemere trains.
More recently there have been tweaks to remove the worst anomalies, and the stopper has been extended to Harbour, giving it two tph again. But if the future pattern is to be permanently back to the pre-privatisation system of one fast, one slow and one short working, it really needs a proper reworking and a return to 20 minute interval departures. Sadly passenger convenience and logical timetabling seems to be a lower priority than arbitrary cost cutting to whoever currently manages our train services.