its usually due to other countries (and the EU for example) that have higher safety restrictions for phone battery capacity so it can be sold there. like if they ship it as 6800mAh then its gonna have to be classified as a more dangerous device so higher shipping costs end up on the user that is already paying more than most phones so they will just lose money. some companies keep it the same size and pay the extra fees and stuff but others also split up the battery (takes up more space) into smaller pieces that add up to the same mAh so its a workaround. but thats just expensive and time consuming. Xiaomis main market is in china so thats why they prioritise them first. So mainly due to regulations and costs. but also, the chinese version is more optimized for chinese apps because apps like wechat and other things take a lot of power so there isnt really a big difference when it comes to use for international. just double check the info on the internet and correct my info if i'm wrong.
The Xiaomi 17 Ultra is likely still a month or two away from being unveiled internationally. In the meantime, details about this global model have emerged. Sadly, it seems that Xiaomi is preparing to offer the device with a significant downgrade over the model sold in its home market.