Your wiring diagram is correct, your construction is not!
The OEM design meets the following:
1)It connects line an neutral to line and line on the OEM 14-50 EVSE
2)It connects ground to ground on the same
3)it does this with solid brass of large enough size for the current drawn
4) it does the above in a package that is physically robust to prevent exposure to the power if the cord is pulled out and prevents any exposure to of the user to the power
5) and most important is is of a physical shape that only the EVSE 14-50 and no other device that has a 14-50 can plug into it.
Again because it works, doesn't make it right, or safe.
Yours FAILS on 4 and 5, and by the looks 3 also.
You could meet 3 and 4 but did not.
Mounting the 14-50R in a robust box grounding the box if metal, using SJOO 10 ga cable and strain relief on both ends would take care of 3 and 4 but still leaves 5 unaddressed.
You are smart enough to figure out electrical path, but completely ignorant of all the safety engineering that went into the original OEM adapter.
I could use car jumper cables to power my 240 well pump from the main distribution box, and it would work, but it wouldn't be safe, and that is the same thing you are doing.