Perhaps specie was the wrong word.
But humans and chimps/orangutans are different species.
How did they cross-breed?
Why are there no fossils found of these ‘intermediate’ forms?
The idea is that until "speciation" happened, the two (or more) subspecies could interbreed.
Now, regarding "intermediate forms", we don't know that a change of "form" is required at the time of "speciation". You got mom and dad of one species, and junior and his sisters are another ~ but they look pretty much alike ~ maybe identical.