I did notice afterwards that it did go back to normal-ish. Just never seen them go to Redhill/Gatwick from 8 before
It isn't that rare - all of the stopping trains to Redhill between 1048 and 2048 appear to be booked to go from platform 8.
The platforms for Redhill bound services depend on whether a train from Portsmouth is due shortly before the arrival at Redhill in which case they will use platform 8 or shortly after in which case they will use platform 4. Of course, it also depends on whether there is conflict with a Portsmouth bound train in platform 4 or a Reading bound train in platform 8.
Looking at the standard times, Gatwick trains at xx08 are at Redhill at the same time as a Reading bound train using platform 8 at xx09 so typically use platform 4. Redhill trains at xx48 arrive just after a Reading departure and a train from Portsmouth (xx49 to Waterloo) so using platform 8 makes sense
