While I can’t give you a definitive reason this specific lens has not been supported yet, I can tell you that on average it takes two to three months for a newly released lens to be supported once the lens becomes available. Support by DxO requires access to a loaner copy of the lens. The number of loaners available in Europe and the number of other testers also waiting for a copy of it to test can further impact how long it takes for support to be added. This is further compounded by the timing. New camera/lens support is not provided in July and August as DxO finalizes the release of the new version of PhotoLab which should be available in September.
I just checked @Marie’s most recent post on upcoming support and found that support for your lens will be added in the second group of lenses this fall. It is unclear exactly when that will be.