Your reference supports what I said.
“The existence of these fictitious forces apparently provides a means of detecting a non-inertial frame. In other words, accelerated motion appears have an absolute existence, whereas linear motion is always relative (to another object). Another example is provided by Newton’s water bucket experiment (C&N p. 403). If the bucket and its contents are rotating at the end of a long rope, the water surface will become curved, due to the centifugal force (according to ab observer rotating with the bucket). Observation of this curvature provides direct evidence that the system is rotating, without reference to any external object. However, Newton’s explanation was rejected on philosophical grounds by the German philosopher Ernst Mach (1838-1916), who maintained that motion of any kind (linear or rotational) can have no real existence unless specified with respect to other objects. So what other objects define the rotation of a water bucket and cause the water surface to become curved ? According to Mach, the rotation must be defined relative to the rest of the universe, including stars and galaxies at immense distances which together exert a force on the water. Satellite experiments designed to detect such a force, arising from the acceleration of one object relative to another, have been partially successful.”