I don't recall ever hearing of anything like that but if these are truly returns (you need to make sure they are) it sounds like someone overthought their system and wanted to have floor returns in one season and upper wall returns in the other. You need to make sure what they are first, then we can deal with how to address it.

Here is a link that might be useful: Air Conditioning and Heating Repair Made Easy

In my old house there were two registers in each room--one high and one low. The high was open in summer (for AC) and the low in winter (for heat). But there was only one return.

If in fact they are returns, then you would open the floor one in winter (to remove the cooler air as it falls) and the ceiling one in summer (to remove the warmer air as it rises).