Is exactly what is done with services, feeders, and multiwire branch circuits, we do not run a separate "neutral" for each "phase conductor". We also do not run a neutral if the circuit doesn't utilize a neutral connection. Exception being the service still needs a "grounded" conductor by code if the system has a grounded conductor, but we do not have to extend it to equipment that doesn't utilize it.
Gotcha, my biggest hangup on the whole thing was like others have mentioned that its not a good idea to disregard the termination and strain relief capacities of a plug or connector.
The splitter i made disregards both limitations.
I dont see anything unsafe about it, but in the event of a failure of any kind in the assembly, it can very easily be blamed on the assembly method and that the manufacturer guidelines were not followed.
However,
If i were to sell such an adapter and provide full disclosure on the assembly and a no liability disclaimer, i feel like the seller is in the clear and it is the recipient's responsibility to use and connect the assembly properly and to not exceed the max load capable of the assembly.
When purchasing an extension cord from any retailer, the purchaser is given a max rating in the instructions for the cord and its up to the buyer to use the cord responsibly and place under a load that does not exceed its capability. If you fried any cord manufacturers cord or exceeded its capacity and that damaged your equipment, that company themselves are not liable or responsible for the damage to your equipment or personnel-(God Forbid).
It can very easily be argued that the assembly was not used in accordance with that companies instructions for that cord assembly. Like i said before there are a lot of grey areas when it comes to custom power cord assembly and why UL will absolutely not list anything but a cord assembly that is the same volt, amp, and pole count on both sides of the assembly.
If there are companies selling assemblies that start dropping legs or going from three to four pole and stuff like that, UL wants nothing to do with it and encourages people to stay away from such things because they are not "Listable"
Anybody selling such configurations and claiming that it is a "UL Listed" product is
Fraudulently selling that assembly.
When a customer of such an assembly is made aware that it is not a "UL Listed" assembly and purchases the assembly with that knowledge, the manufacturer should give instructions and ratings for the assemblies and if they are exceeded or if failure occurs due to misuse, that company should not be held liable. If it can be proven that the assembly was wired incorrectly however i would expect that any respectable seller will accept the responsibility and compensate accordingly.