Most organisms use their skin to protect them from the environment. Amphibians use their skin as an interface to the environment. That makes them particularly susceptible to a wide variety of chemicals.

I have seen studies of glyphosate (RoundUp) being toxic to frogs and other amphibians. I have also seen studies of SOME surfactants also being toxic to those organisms.

However, your questions are now above my pay-grade! There are several biologists on the forum, and a few chemicals experts. Maybe they will drop into your thread.

If you don't get your questions answered, then you may have to resort to experimental science. You could try treating a very small area of the bank. On most toxic chemicals the "poison is in the dosage". If only tiny amounts of "pond approved" herbicides get in the water, hopefully you will not impact your beneficial organisms.

Another option is to chase out all of the organisms in the area to be treated. You walk through several times, or throw the tennis ball into that patch of weeds until your dog gets tired retrieving. That may exclude all of the amphibians from the treatment area and they will escape the direct effects of the sprayed formulations.