Currently, the return message from the inventory import report is in pt-BR. So when the import is finished, the email triggered through the template "relatorio-de-importacao-de-estoque" has the information in pt-BR, not considering the store locale.

1. Access the inventory import (Orders > Inventory & Shipping > Shipping Strategy > Warehouses > Import Items);
2. Attach the file to be imported;
3. At the end of the importing process, the e-mail will be sent with the import result. We can see that the message is not respecting the language of the account:

"Importação concluída! Total de itens importados: 6. Total de itens não importados: 0."

There is no workaround.