"The pier had been used by the Kowloon Customs sub-station (1887 – 1898), Chinese Labourers’ Quarters (1904 – 1906) and Quarantine Station (1908 – 1910s) for boat parking. Its role gradually faded out when land reclamation began in 1921 in Lai Chi [Kok] Bay." Source: "Research Study and Heritage Interpretation of Historic Relics in Jao Tsung-I Academy" (2017), https://www.jtia.hk/wp-content/uploads/2017/07/lw_paper_eng_120.pdf (p.16) (see also the lower photo on p.17 and site plan on p.30)
"Traces of history can be found inside High Zone, such as the ancient pier, one of the oldest heritage remains in the area". Source: "Past and Present: Stories of the Site of Jao Tsung-I Academy" (2018) p.77.
The current location of the pier is shown on the Heritage Trail site map of Jao Tsung-I Academy ( lord-wilson-leaflet_eng-_-download.pdf) but this is yet to be confirmed.
Comments
Old stone pier(s)
The maps at https://www.hkmaps.hk/mapviewer.html that show this area clearly are:
dating of old stone pier
The source for the information about the early days of the Kowloon Customs service is given in the JTIA research report (2017) as 九龍海關編志辦公室編：九龍海關百年大事記 1887-1986 （修改 稿).
If the pier does date back to 1887 or before, it does seem odd that no pier is marked on the pre-1904 maps. I would also have thought it would be located near the Low Zone rather than the High Zone of the site.