An interleave of 0 and an ets_cycles of 8 is not a valid setting for ETS. Interleave specifys the number of waveforms to select out of the number of ets_cycles. For example, setting an interleave of 10 and an ets_cycles of 100 would mean that the device would aquire 100 waveforms (ets_cycles) and return to the user the 'best' 10 waveforms out of these 100.
ETS does not perform any averaging on the waveforms, but rather returns several waveforms interveleaved together each one offset in time by the correct amount.
You are correct that oversampling reduces high frequency components of the signal, but this attenuation begins before the Nyquist limit is reached and gets progressively larger the higher the input frequency (up to Nyquist). The higher the setting for oversample the greater this low pass filtering effect is.
Are you interested in reducing the low frequency components of your signal only while maintaining the amplitude of the higher frequency components? For that you would probably need to look at high pass digital filters.
All the best