Yeah that one particular study isn’t perfect, but I think the follow ups with community reporting that Laura posted are collectively better. https://www.bund-lemgo.de/apfelallergie.html
Also I started a new thread for all of this here: https://goingtoseed.discourse.group/t/breeding-apples-from-ancient-apples-for-people-allergic-to-raw-apples/3579
The thoughts on rootstock perhaps affecting the phenolic acid content is definitely a good theory to test as well. I haven’t been able to taste any ancient varietals yet but I’m excited to try them. A friend said there’s a rural apple festival close to Johnson City (I’m in Knoxville) and I will try to visit an orchard or two in advance to make some apple grower contacts. I’ll copy this to the new thread.