Hot and "warm" Jupiters expelling terrestrial planets?
It's not proof that they've ejected other inner planets, because there are plenty of other explanations for why we haven't observed companions. Steffen et al. (2012) analyzed Kepler data - likely some of the same examples you've looked at - and came up with several explanations besides the no-companions-because-of-planet-planet scattering hypothesis:


Inner planets never formed. It's possible that mechanisms in systems with hot Jupiters prevent inner planets from forming; the authors are unclear as to what those mechanisms might be.
The planets are too small to see during transits. This is the first explanation based on detection bias. Obviously, Kepler has its limits, and it's entirely possible that the systems have small bodies it simply can't detect.
The planets are too low-mass. It is possible that there may be planets with masses so low that transit-timing variations (TTVs) are too small for Kepler to see them.
The planets have high mutual inclinations. In other words, there might be planets with orbits highly inclined with respect to the hot Jupiters' orbits; we only detect the ones at inclinations favorable to detection from our angle.


The options the authors suggest rest mainly on experimental biases as opposed to theoretical possibilities.

Something I was confused about when I read your question was the assumption that hot Jupiters migrate mainly due to planet-planet scattering. Levison et al. argue that warm Jupiters (i.e. giant planets with semi-major axes of about 1 AU) are more likely to have migrated via planet-planet scattering, because it provides a stopping mechanism via damping, assuming the planetesimal number density scales appropriately. This happens when the energy needed to move planetesimals from their orbits is greater than the energy lost from the change in the planet's orbit. Given that planetesimals cannot survive long in orbits less than about twice the stellar radius, warm Jupiters reach semi-major axes no lower than 0.03 to 0.1 AU (see Murray et al. (1998)).

Hot Jupiters, on the other hand, may be driven largely by Type II gas disk migration, where giant planets create a gap in a protoplanetary disk that subsequently brings in material; this then brings the planet closer to the star, eventually leading to a hot Jupiter. Here's a visualization, from Planet Hunters: