It does not say "The Complete Fifth Season" on my packaging just "The Fifth Season". I don't know if this is illegal but it's certainly misleading. It should read "The Fifth Season: Part One". I must say I am very disappointed about this, I may wait to watch this until I get part 2 which will be some time.
I feel this is misleading and likely contrary to the sale of goods act and trades descriptions act. I am considering forwarding the facts on this situation to the Trading Standards Authority in the UK Breaking Bad - Season 5 [DVD]