This only a surprising thing because a human would parse the waveform as two words and then back into a single concept. A computer could parse it as a single concept directly or in syllable lengthed chunks to be reconfigured however.
A human really wouldn't. It's the same thing as telling the difference between black bird and blackbird in running speech; peanut butter may be spelled as two words, but it's spoken as a single thing. If the concept was new enough that you were consciously talking about a type of butter made from (of all things) peanuts, it would be a black bird vocal entity rather than a blackbird one.
You're still talking about words, but the issue is waveform sound. An english speaker would hear "black bird" and use rhythm and context clues to parse it into words and then into the appropriate idea. A non-english speaker might hear something like "blekabirt" as the waveform sound is interpreted through their particular linguistic habits, then it would be rejected as a non-word sound
It's true that we do alter our speech to provide context clues, it is also true that without them we're _still_ capable of piecing them together.
If someone says in a unnaturally drawn out way "I like peanut butter sandwhiches" then I will have no problem detecting the situation and then re-parsing it correctly.
Your brain thinks of these two words completely differently and it's only through conscious effort that you think of them together. They are different words even though they sound and are spelled the same, regardless of the space.
A better example I think is "bear feet" vs "bare feet"
"Blackbird" refers to several species of actual bird, not just the plane. "The black bird ate seeds" and "The blackbird ate seeds" are both reasonable sentences, and they do potentially sound different.
I'm not convinced. It takes effort for me to break apart blackbird into two separate words in my head, as they are so commonly found together. When speaking "black bird" I would insert a long pause between the two and emphasise the "b" on bird to show that I'm not talking about a "blackbird".
