I have driven small engine cars (~1.5 L to 2.5 L) for 30 years. They all consumed oil, typically at about 1 qt/2500 miles. My 1.8L acura integra burns 1 qt every 2500 miles or so and has done so since 1990, more 125,000 miles ago. The engine is just as strong and reliable as the day I bought it. My 2.5 L BMW runs about the same engine speed (actually a little slower)as the 1.8 L acura so I would not be surprised to see it use some oil too.
BMW says that I will have to pay for the oil top up, but surely if a top up is needed already then potentially it was not full to start with?