Can you imagine the bravery of the dogs that were used in these bear hunts. To see an animal 6 times their size and still seize upon it. What heart they had. Very few dogs today would take up this challenge.
Yes, they were more brave up to the addition of "alpine mastiff blood" to the Mastiff to increase the size, genetically is more molosser the current bulldog than the Mastiff, for a small DNA advantage, second is the Boxer, and third the Mastiff which is now equal to the bullterrier miniature. Genetics speaks... and put away historic references.
The Tosa absorbed the best of the molosser bloods, and most be similar to the current Mastiff in their genetics, because the base was an Akita like spitz dog. That means that the Tosa has primitive wolfish and molosser blood like the Bulldog.