No, additional coupling or internal noise is not expected of the HMC1119 part at low power.
HMC1119
Recommended for New Designs
The HMC1119 is a broadband, highly accurate, 7-bit digital
attenuator, operating from 0.1 GHz to 6.0 GHz with 31.5 dB
attenuation control range in 0.25...
Datasheet
HMC1119 on Analog.com
No, additional coupling or internal noise is not expected of the HMC1119 part at low power.