It's not always true that biologists reject differential equations! The Hodgkin-Huxley biophysical model of neural firing, developed in the 50s, is extremely mathy and extremely differential equations-y and is still canonical, though not widely used in practice.
When I asked Claude about Rashevsky vs Hodgkin-Huxley, he (it? they?) suggested that the elements of Hodgkin-Huxley were more closely tied to physical biology than Rashevsky's work, which was more abstract. So maybe, as you say, Rashevsky was in a middle ground; too complicated to be computationally useful, not complicated enough to be properly biological.
It's not always true that biologists reject differential equations! The Hodgkin-Huxley biophysical model of neural firing, developed in the 50s, is extremely mathy and extremely differential equations-y and is still canonical, though not widely used in practice.
When I asked Claude about Rashevsky vs Hodgkin-Huxley, he (it? they?) suggested that the elements of Hodgkin-Huxley were more closely tied to physical biology than Rashevsky's work, which was more abstract. So maybe, as you say, Rashevsky was in a middle ground; too complicated to be computationally useful, not complicated enough to be properly biological.
https://claude.ai/share/41374733-4e11-448e-964e-159f4986f31d
(That conversation also reveals that I forgot the name of the Hodgkin-Huxley model. It was a long time ago!)