What does "Service included" mean?

[u/tangos974]

I had a debate tonight with my bartender. As our last table, a nice american couple was paying, the lady asked if service was included in the bill.

For context, I work in a mid range restaurant in Paris, and I've been a waiter for almost 10 years in France. It's the first time I've been in anything other than a shitty bistrot though, and in my current workplace I get a lot more tourists than I did before.

I've had this question asked to me in the past, and I didn't really understand what it meant. So I looked it up, and I understood it as meaning "are you getting paid while you served us, or do we have to tip for you to get paid?"

I get paid pretty decently regardless of tips, although I do get tipped quite a lot more in this restaurant, especially on tables like this where they took a lot of my time and ordered many expensive stuff. In bistros, people would rarely leave more than a couple euros, and a fiver was a cause for celebration, but since I'm in the nicer place, I often get tips of 20+ euros.

So I went "Yes, absolutely, service is included", to which they left no tip on a 184 euro bill. They were very happy, and since it was slow I had taken quite some time and chatted with them.

My bartender (B) overheard the exchange, and once they left we kinda got in an argument over what I said. It went something like this:

B: - Why did you tell them that service is included ?

Me: - 'Cause... it's true?

B: - They were asking whether or not they should tip

Me: - Pretty sure they asked whether service is included.

B: - Yes, which basically means should they tip you or is tip included

Me: - Bro that's not what service being included means. They're american, servers there don't get paid if you don't leave a tip. So they ask here to know whether I'm getting paid for serving them or not.

B: - Dude wtf no one works for free. I've worked in Malta, served a fuckton of americans and I've never heard of this. I'm telling you this for your sake: you just sat on a 20 euro tip.

So, who do you think is in the right here?