Such frank talk is difficult. But it will lead to more understanding and certainty for you and your regular vet. Simply changing clinics or putting up with more uneasiness about your encounters with the clinic doesn't seem productive, at least not without clearing the air. That book was published in 1974. That vision is not inhibited is one differentiation from cataracts.
All dogs develop lenticular sclerosis as they age.
Few form cataracts. Sclerosis is bilaterally symmetric, cataracts do not need to be. True cataracts obscure ophthalmoscopic exam of the fundus of the eye. A sclerotic lens still allows visualization of the fundus. A veterinary eye specialist can discern which part of the lens is involved in cataract formation.