I honestly think HR on scopes is overrated.. How many times you have to observe a perfectly repetitive signal upon which to oversample?
Many times you don't have a precise idea about what you are going to observe, and turning HR on could mask the real stuff you want to see...
HiRes (ERES) is not same as Averaging mode...
AFAIK the HR modes are more or less implemented as follows (but please correct me if I'm wrong):
Pre-Filter --> Over-Sample --> Average --> Data-Thinning --> Filter
Not really.
That doesn't explain what is being processed and how.
In scope parlance Averaging is averaging same data points from different trigger events. Good only for repetitive signals. It does not lowpass filter signal.
Hires is a running average lowpass filter. It trading temporal resolution for amplitude one.
ERES is alternative implementation of lowpass filter with better impulse response..
There is no "data thinning"(we call it decimation) as a separate step anywhere, nor Pre-filter ..
There is also no oversampling but we simply sample as a scope normally would and than apply transformation.
On some scopes (LeCroy, some Siglent) ERES is available as a math function, so you retain original data and can apply it after the fact.
Search internet for ERES whitepapers by Lecroy. They explain it better than I ever could.