A) Rule that the device automatically succeeds in opening the safe, regardless of the DN normally required to open it. In effect, allowing a DN 10 Science test to replace a DN 16 Locking Picking test.
B) Rule that an additional Lock Picking test is required to open the safe, in which case the successfully created and working weird science device provides absolutely no benefit.
A is not how it works; the text even says as much. "On a success the device functions and can be used to overcome the hero’s problem, though this may require additional skill tests (e.g. lockpicking or air vehicles)."
B is not how it works, either. The examples of using the perk are: "picking an unpickable lock, hang gliding off a cliff, or making an improvised weapon." The lock wasn't pickable without the device. Creating the device (assuming it works, which it may not) makes the lockpicking test possible in the first place.
(or what ZorValachan said)
It appears that you're picturing the use of the perk as a way to get a bonus on a task that the PCs could already accomplish. When the perk, it seems to me, is actually about coming up with out-of-the-box solutions to problems by making the impossible, possible.