A hole is a hole is a hole ... the NEC makes no distinction as to size.
But ... will you still have a wall? Or, have you now made it something more comparable to, say, the partition within a cabinet?
Let's look, instead, at what the code is likely to have had in mind. Here are two examples:
In this example, the cord passes through a tiny hole in the stair riser, to power a lamp in the closet under the stairs.
I might see three basic problems with this arrangement: using a cord in place of a permanent wiring method, the obvious trip hazard, and the risk of damage to the cord, as it rubs on the hole.
This example is a bit different. Here, the cord passes through a small - maybe 2" - where the two walls fail to meet. Yet, that cord turns out to come from the back side of the furnace (for the igniter).Should you wish to service the furnace, you have no way to access the plug to disconnect it ..... and there is a locked door between the two areas. (Actually, several doors).
So, I'd say we have two major concerns to address:
1) You need to be able to shut something off, preferably from where you will be when you want to work on it, move it, etc.; and,
2) The cord, AND plug, needs to be able to pass through the opening, and the opening has to be free of any edges that might damage the cord.
Only you will be in a position to honestly answer these questions. If nothing else ... what will happen when the fridge is pulled out to clean under it? Will you run out of cord, and be yanking on it? Will you be able to reach behind the fridge - from your position in front of it - and unplug it?
After all, that plug is the disconnecting meand, and generally must remain accessible.