“A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are often used, such as similarity of DNA, morphology or ecological niche.”
Wiki
Sounds like the definition of what separates a species from a sub-species isn’t all that precise .
Reality, as is usual, doesn't like to comport well with being assigned either or little boxes and hew perfectly to set definitions.
Say you walk from a forest into a swamp, where do you draw the line between, is there such a thing as a swampforest?
;)