Improving low valve lift flow

Hysteric said
What's the direction of flow with a large valve curtain area and very little piston demand all the while the exhaust gasses are looking for somewhere to go?

Put another way what's the piston speed around the overlap period to create the demand for it to flow in the first place?
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The op asked a generic question I gave a generic answer.
When talking reversion there are many things to consider valve timing , exhaust, intake type, on and on.
Is reversion a problem with a stock engine? stock cylinder head?