@Tarek > I'm guessing this was made possible so as to enable the traffic light system through standard notation. If you wish to benefit from this, I would encourage you to get MiK to write the tags to the Comments field and then have rekordbox analyse the key.
I will, of course, report this to the dev team.
To re-analyse tracks simply right click them and choose Re-Analyse. Select multiple tracks to re-analyse them in batches.
By first beat marker, do you mean the red beat indicating the start of a bar? This is a rekordbox update that has been added automatically.