Rawrly saidIt appears in scientific papers. Use the scholar search function on Google, for instance.
Well I did, and in no cases was the phrase "inbred vigor" a title. A typical title would be:
Hybrid vigor in Pacific oysters: an experimental approach using crosses among inbred lines
Male gametophyte in maize: II. Pollen vigor in inbred plants
If you search the exact phrase in text, it's only in maize.
If it exists, it's demonstrated only in plants and exceedingly rare.
Whereas hybrid vigor is demonstrated many times in both plants and animals.