Seeking clarification on Capacity of Bluetooth Data Collection (without using Beacons)

My understanding is that the capacity of the Bluetooth data source is to scan and monitor Bluetooth signals in the surrounding environment and that only by using beacons can we capture proximity and contact patterns. However, I noticed that in some previous publications it seems smartphones with the app were able to detect the proximity of one another without the use of beacons. For example, there is a study that states “Bluetooth detection of one smartphone by another was used to estimate the likelihood that any two iEpi sub-study participant smartphones were within a few meters of each other during the course of the intervention period.” ( With the Ethica app is it possible to see when two smartphones with the app are in Bluetooth proximity of one another without the use of beacons?