Used to play this loads

I am absolutely sure there used to be unrevealed maps/fog of war, especially for campaigns.

Is this missing, or am I going insane? =D

Depends on the map you play. Some have fog of war on, others don't. In Bane Wars I don't think there was fog of war except possibly for the last mission, but even that I don't think so.

If you play random, you have an option to switch the fog of war on and off.

And, as far as I can tell, gog version has fog of war just the same way the disk version had.

A small number of maps in the Bane Wars campaign did have Hidden Map active, but none of the campaign maps had Fog of War active.

Both options were available for toggling when not playing the campaign.

This was changed by the fan patch.

In W3DLR it is called 'Hidden Map' and can be toggled on/off in the Option menu if you play custom game. In campaigns it's OFF in most scenarios and is ON in few crucial ones to make 'em more difficult to win.