Likewise, welcome, JPK.
I think it may depend on what school the LA. attends. Maybe in areas like Maryland, which has fantastic old trees everywhere, they do a good job of educating them about tree needs. In areas where most trees are still young-middle aged, they don't seem to pay as much attention. Here in Colorado, for instance, the state schools require exactly 0 hours of horticulture for the degree, (or so I've been told; someone please correct me if I'm wrong.)
And you're right, one shouldn't generalize, but...my experience has been that most of them, locally, emphasize the aesthetics of their plan over the health of existing plants. They design grade changes, irrigation lines across major roots, roto-tilling over shallow rooted trees, metal edging through roots, etc. etc. One of my best clients has lost two monumental maple trees due to poor design by one of the area's most renowned LAs.
If I'm designing changes to an existing landscape, the first order of business is preserving the desirable trees, integrating them
into a design that doesn't kill them.