Acronyms under most English style guides should be written in lowercase with the first letter capitalized. Only initialisms should be in all caps, which Aldi is definitely not.
I almost always see most acronyms (not brands with an acronym origin like Aldi) in all caps, and always considered it an odd quirk of the BBC that they did not.
Editors will make exceptions to general style guidelines when they think it leads to better clarity when reading. For instance, most newspapers will write iPhone with a lower case 'i', despite that being incorrect for a proper noun, because people are used to seeing it that way.
e.g. https://www.nytimes.com/2023/08/17/business/aldi-winn-dixie-...
e.g. https://www.bbc.com/news/business-63015985
Aldi's corporate style is "ALDI" but that's just their internal guidance, not the rules of English.