According to the Wikipedia article on GNSS positioning calculation, GNSS-based positioning needs $t_\text{satellite}−t_\text{receiver}$ for a series of satellites, along with the satellite positions. This is an element of trilateration. However, the clock in a GNSS-receiver is not atomic, and not nearly accurate enough to determine $t_\text{receiver}$ with sufficient accuracy for trilateration. Therefore, it needs a 4th source to determine the time, such as indicated by maptoaster.com or this Yahoo Answers post. That makes sense: it simulatenously determines time, latitude, longitude, and elevation, and therefore it needs four satellites.
Why, then, do we still consider this positioning trilateration rather than multilateration? In my understanding, A GNSS receiver does not need a clock at all — after all, the clock that it has, is not nearly good enough. Isn't the implication that it's using the difference between the distances to the satellites for positioning — the principle of multilateration? Yet the latter Wikipedia article states that:
Multilateration should not be confused with trilateration, which uses distances or absolute measurements of time-of-flight from three or more sites, or with triangulation, which uses the measurement of absolute angles. Both of these systems are also commonly used with radio navigation systems; trilateration is the basis of GPS.
Is GNSS-based positioning considered trilateration or multilateration? Why?