I've seen a row of 20 active e-passport gates and maybe 1 or 2 officers in their booths off to the side, both assessing people in their role as a second line of

I've seen a row of 20 active e-passport gates and maybe 1 or 2 officers in their booths off to the side, both assessing people in their role as a second line of assessment (I've before had the gates fail to scan my passport and had to go to the booth). At least in those circumstances, it doesn't seem to be the case – both because I don't think a 1-10 ratio would work, and because they were busy doing other things. Maybe this happens in some places, but as far as I can tell, not in the UK/Heathrow or Australia/Melbourne where I use these gates regularly.