The example used here is for Murawai Beach, 11km north of Anawhata.
This is a common question. The Metservice tide forecast is based on LINZ tide forecast, which uses known tide times at standard ports and then applies an offset for 'secondary ports' - for example, Muriwai Beach. These offset values are often approximate.
The NIWA tide forecast is predicted by a purpose built tide model designed to calculate the tide at any location of open coast (not harbours) around New Zealand. The NIWA tide model has a stated accuracy of +/- 10 mins.