I would say the developer has thought about their own requirements and knowledge, much like you have in your comment by thinking only of Europe whereas pretty much every other country/region in the world uses metric.
Whilst creating an application that deals with different units is not a massive amount of extra work, launching a minimal viable product to 300 million people in a country that has a major obesity problem is probably not a bad start. And when I say not a lot of extra work, 2-4 hours depending on experience of units, server side and client side, data store, would be very optimistic, hundreds if you are moving towards a more complex project. Quite a bit on top of what was only a weekend project.
Whilst creating an application that deals with different units is not a massive amount of extra work, launching a minimal viable product to 300 million people in a country that has a major obesity problem is probably not a bad start. And when I say not a lot of extra work, 2-4 hours depending on experience of units, server side and client side, data store, would be very optimistic, hundreds if you are moving towards a more complex project. Quite a bit on top of what was only a weekend project.