On another forum, one careful reader has pointed out that the description actually states
"To start your vacation with a toast, our Cabin Crew will be offering you a complimentary glass of sparkling wine"
He's used the internet archive to find an earlier version, which has
Complimentary welcome glass of sparkling wine along with other complimentary stuff like meals and face towels.
So champagne service is a name of a service category, not necessarily a promise to supply actual champagne. He points out that being a gold service member with a car hire firm doesn't reward him with actual gold, and he hasn't got any platinum from a hotel chain.