The alternate name for that Dusterlohe, is 'Nicky'. It is rather nice, if you get the real one.
Apparently, taking good care of your Phlox paniculata, even including older varieties, helps to prevent powdery mildew.
I've see comparison was done, (albeit, many years ago,) & even 'Katherine' did quite well, compared to 'David'. You may want to look for her.
I noticed one vendor here, for 'Katherine' fairly quick.
While I'm not so sure why 'Fujyama', isn't so readily available, here in the U.S. as it has AGM, by RHS.
Have a look in the Database here, for the real 'Blue Paradise'. This way, you'll know what it ought to look like, if you can buy a potted one, while in bloom.
As for 'Blue Boy', it must not have been a Phlox paniculata, being all that much of a memorable bloom, to me.
I think 'Eva Cullum' may have been another very nice looking cultivar.
