Official comment
@Ramez > Tracks loaded from the FOLDERS scope have not been analysed / exported by rekordbox. Any waveform that the player displays on track load is coming from a stored memory of having loaded / played that track previously where it was able to read and build a waveform, then store it, the same way a CDJ-1000 did to an SD card for CD audio. What you're experiencing is a track you've played before is able to call up that data and presto --waveform and BPM.
If you want all that information to show immediately, export it from rekordbox and browse everything other than "FOLDER"