Yes, your Lockpicking skill is going against the difficulty level of the actual locks on the boxes, not the boxes themselves, and this is connected to your tinkering. You will see a message when you create a box that says something about you having sufficient Tinkering skill to lock it, or something like that. You can have next to no Carpentry to make small boxes and that's fine. It's the Tinkering skill.
It can be annoying to create a character with the exact correct Tinkering skill but it's pretty much the way it goes with Lockpicking.
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