The key difference is that if a product is shipped directly to you from outside the US, you'll be responsible for any import fees if the seller doesn't pay them. Some sellers try to get around these fees by mislabeling what they're shipping so...
If you'd like to buy from the US and avoid any Mini 5 Pros being imported as "cordless drills", which would leave you responsible for import fees if discovered, there are some US sellers on eBay. And you can also find a few on Amazon as mentioned...
Just to clear up any confusion, DJI doesn't make an "EU battery" or sell "EU combos". You're referring to the standard Mini 5 Pro battery.
DJI has always offered two options, the standard Mini "Battery" and the Mini "Battery Plus". The Battery...