Likely. I too suspect this is a cost-saving measure realized by halving the processing and powering requirements, regardless of the actual physical implementation.
Consider it to be somewhat analogous to the older non-auto-switching mode of recording a second set of safety tracks at lower level. Engaging that mode requires a second set of ADC channel paths and recorded output channels, but because no additional ADC>output-file channel paths are available, it cut the available recorded channel count in half. Very similar behavior.
Zoom and SD could have similarly limited the number of inputs when set to record 32-bit float mode, however the SD series II and Zoom F8 "Pro" generation recorders were designed with sufficient resources to be able to support "auto gain/ADC switching" at full input channel count.