Yes it is. Announcements that Oyster is not valid should not be played on services that operate wholly within the Oyster area.
But it's not the most pressing issue when we see constant calamitous breaks in the service to Heathrow (and elsewhere), ever since the last upgrade. It's starting to get into aviation articles about Heathrow, it was never an issue on the Piccadilly, the HEx used to go through periodic patches, but not like we have had since the integrated Liz running started.
And I don't want to say 'told you so' about the auto-reverse at Westbourne Park inevitably giving trouble, but ...
For goodness sake, there are three reversing sidings there. Surely that is adequate for the drivers to walk through a walk-through train and set up the opposite cab without this over-clever silly stuff.