Not to be pedantic, but are you sure there is nothing else on that same circuit? Its very rare to have a single circuit breaker feeding just one light. 
In addition to that, I believe the Inovelli 3-way/4-way implementation is also going to use some additional power in order to sense the position of the 3-way/4-way slave switch. 
With that said, I’m just speculating all this and it would be nice to get some official specs from Inovelli regarding what the expected ‘idle power draw’ should be. The spec sheet shows what the maximum wattage is, but not the idle or off-state wattage. 