For example people will often say give me that liter of wine, when in fact the bottle it’s 750ml and not a liter per se.
No one has ever said this. Ever. In the history of ever.
Wine and spirits in the US were sold as "fifths" or one fifth of a US gallon, equal to 757ml. This became a "metric fifth" or 750ml. No one is even slightly confused by this.
1. By the bottle. Bottles are usually 750ml, but 700ml and 1000ml are not that rare. In any case, you bought that bottle of that specific wine brand/year. The quantity is whatever the producer decided. The price is per bottle and quantity doesn't factor in.
2. By volume. This is only used when you buy in bulk. You go to a winery where they have huge barrels with a faucet. You can taste the wine and then buy any quantity you want (you can even bring your own container).
I understand what you're saying, but it's a bit disappointing that the company doesn't train their salespeople to understand the bullet points they're trying to sell. This isn't really CCNA-level knowledge.