Simple.
The complex nature of contemporary eyepiece design allows for many modern eyepieces to be designed to work virtually equally well between different scope designs (variations in performance with individual focal lengths will happen across different scope designs). This is also testament to the clever designs that have been developed for these lines. The LVW's that were mentioned were a particular favourite of mine because of this reason. I have always said this too. If any doubt, I suggest one do a search for all my discussion about the LVW line. No misrepresentation on my part.
What all these eyepieces have in common is they are pricey.
Similarly, like I said in post No. 16, between EPs designed for a particular scope design, say a refractor, the majority of focal lengths in that line may not perform well in a Newt. However, there will be individual focal lengths that will perform very, very well in Newts. This is not to say that they will perform the same as a Nagler, but for a fraction of the cost the end user may be very happy with that more modestly priced eyepiece, even if the very edge may show a small amount of astigmatism.
What these eyepieces can offer is very good performance in a Newt for not so large a price tag - those inexpensive gems.
Some bedtime reading:
https://www.telescope-optics.net/ind...LE_OF_CONTENTS
Discusses different scope designs with their pros, cons and inherent aberrations, plus eyepieces, their designs, aberrations and relationship with scopes.