Tremorsense- Just Darkvision?

Having used a human Shadow Tamer, i've had a chance to test the Tremorsense ability granted by Know the Darkness. From my experience, there are 2 problems with how it is implemented:

1. It allows you to see flying enemies in the dark, which it shouldn't. 

2. It does not let yoy see invisible enemies on the ground, which it should.

It seems that the Shadow Tamer's tremorsense is implemented as darkvision rather than actual tremorsense.