Doesn’t it eventually devolve to an art, especially at transitions?
All science is an art. The idea that science is clear-cut and there are always definitive answers is mostly propaganda meant for mass consumption. In the real world, it’s not so simple.
Also, there are no “transitions.” There is a continuum, where specimens taken at various intervals might be different, but there is no point at which one can say “it was this; now it’s that.”