Steps to reproduce this issue:
Place two chests to get a large chest.
Block all faces except the sides (use glass or it can’t be opened)
Summon a copper golem and let it interact with the large chest.
Expected result:
The copper golem can open the large chest from both sides.
Actual result:
The copper golem can only interact with the side of a large chest that was placed first
Can confirm, if the first chest placed is obstructed, the golem will not interact with the double chest. An efficient sorting system will heavily depend on this feature, but it has some workarounds, like allowing the copper golem to access both sides while restraining its movement with trap doors for example. As long as the chest is visible and at range of 1 block, the golem will search it.