I'm beginning to wonder about Samsung and there support for the up to date models I have the tab s3 and the note 8 and both seem to be lagging behind with updates
Samsung decided with some models to skip 7.1.1 and go right to Oreo (8.0). I'm not sure where the Tab S3 falls in there but I imagine this applies as well.
Why did the Tab A get 7.1.1? Because that's likely the last platform update for that device.