Jim, your "hunch" is incorrect. I present some evidence; I do hope you'll consider it:
Eric B & Rakim -
Follow the Leader
Slick Rick -
Children's Story
Nas -
NY State of Mind
GZA -
Gold
OutKast -
ATLiens
Organized Konfusion -
Bring It On
The Roots -
Here I Come
Clipse -
Mr. Me Too
Kendrick Lamar -
Swimming Pools (Drank)
As you will see from these samples, good rappers are in touch with natural rhythms and stress patterns and are able to wrap them around the beat. Undoubtedly, lesser rappers will stretch words to fit a recalcitrant context. I wonder who else does that...