According to the French forum, intergrading is the product of two subspecies, while the hybrid is the product of two different species.

Example:
T. Sirtalis "Titi" X T. Sirtalis "Toto" = intergrade.
Proximus T. X T. Radix = hybrid.

Maybe we do not actually use the same definitions.
It should also differentiate between fertils hybrids or not.

Napta