I'm not sure it's a good idea to read too much in to anything on Traveline at the moment.
Apologies if I'm stating the obvious, but bus operators are currently being allowed to change services without the usual notice periods for service registration - initially this emergency relaxation was valid until the end of August, it was later changed to the end of September.
The weekend of 29/30 August, as well as being bank holiday weekend, is the weekend before new school term starts (most schools are intending to start up some time in the following week), and I expect most operators will be putting new timetables in place. There's no hard and fast rule which day of the week new timetables / schedules start, some operators start the week on a Saturday, some on a Sunday, some on a Monday.
There could be something more to it, but most likely explanation is that the current timetables are valid until 28 August, they are expecting new timetables from 29 August but they are not ready to release yet and they want to make this clear.
