This has been on my mind for years.
I was helping a "student" with some stuff their actual teacher assigned, and...
I mean, come on. Half of Wohlfahrt's 60 etudes are just worse versions of Kreutzer etudes from decades earlier!
Wohlfarht has a very nice book of progressive duets for beginner + teacher. They're very well done. Maybe he got lazy at some point.
Half of my own teaching is just a worse version of what I did years ago.
Half of my practicing (it's the better half, I suppose) might be a worse version of what folks like Pinchas Zukerman used to do at age 5....?
Cotton, what would be really interesting would be to read detailed analyses of those Wohfarht studies you are cautious about, compared, of course, with the Kreutzer etudes you consider to be more useful.
If you think Vole-fart is bad, try Sitt or Alard studies. Woof.
And never forget Schradieck, Ševcík, Rode, Spohr, Küchler, Mazas, ... It doesnt matter that much. Some of them may be more "musical", and others more "pure technical training", but in the end they had similar goals. It's natural that one finds parallels in them.
I prefer those excellent etudes of Mazas and Kreutzer too; but Wohlfahrt was standard when I was a beginning student, long ago, and I remember that I quite enjoyed playing some of them.