There are only 24 tables i think, so it is possible that they were genuinely gone. Also your 10 o’clock may not be the systems 10 o’clock. My missus tries to book tennis centre and if she hasn’t done it within a minute of the system opening the all 28 places can be gone.
I do agree though that it seems slightly odd.
Be interesting to see if the same people are at the tables for the Slovenia game. None left then either.