I found a shipwreck map chest that doesn't have a buried treasure map inside. It was in a custom world (sorry, I can't control when I find random bugs) that had all biomes except variants.

How to reproduce: To get the world, click the Import Settings button in the create world menu and add the attached .json file. To find the shipwreck use this command:

/execute in minecraft:overworld run tp @s -134.10 63.00 -518.24 -223.95 21.60

There is a treasure chest and a map chest in it. The map chest should have no buried treasure map.