I think you are right to be wary of new technology, because we have no data on how these products age.
Will they degrade slowly over time or not?
Will they degrade after interaction with plastic sleeves?
Are they robust enough to not be affected by cleaning with microfibre?
I’m in the fortunate position of needing to upgrade my cheap £30 filters (rather than expensive Lees). As things stand, I’m happy to take my chances and be a guinea-pig.
Regarding your use of hard 0.6 and 0.9 ND grads to create a reverse ND grad for dawn/dusk photos, presumably this will work even better with soft grads? Does one stop really make that much of a difference? Would a 0.6 and 1.2 be better?