That’s probably a really good question for someone who is an expert in the diagnosis and treatment of ADHD. From my understanding, you don’t have to have all the ADHD symptoms (including poor working memory) to still have ADHD.
I looked for articles, and I found this: https://www.ncbi.nlm.nih.gov/pubmed/26902180
It references ADHD kids with and without working memory difficulties, so I’d assume that there is a subset of ADHD people who don’t have the issues with working memory. The other symptoms are still there most likely and the ones that need more management.
I would add to that in experience things like memory tend to fluctuate a lot, especially when other symptoms, stimuli, or situations are going on.