As others have said, quite often a "platform alteration" will show up for trains that are booked to use platform 3. From personal experience, platform 3 tends to be used when there are no free platforms. I alighted there a year or so ago when I left a delayed service from Aberystwyth, it did throw me as I didn't know I had to leave the station and then re-enter.

- IIRC unusually platform 6 was being used by a service going to Aberystwyth, 5 was being used by a terminating LM service, 4 was a delayed service to Manchester and 7 was a service to Milford Haven (which I manically had to run for!)
I think when the Cambrian gets its hourly service, platform 3 would be a good place to terminate them - it takes about 1h50 between Shrews and Aber (including trains splitting) so ones on this new service should have more than 10 mins turnaround time because they aren't splitting at Mach - Also, the time between stops is quite generous so it should make it easier to check tickets. Perhaps a ticket gate can be built on platform 3 as they have done at Bath Spa to access the carpark.