RealBeast :
Yes, it does appear that is the case.
Here is what the manufacturer said:
UDIMM just stands for Unbuffered Dual Inline Memory Module or Unbuffered DIMM. All Non-ECC modules are unbuffered, so they are the same modules, just with different.
However, the current working stick says PC3-10600U, and these say PC3-10600.
Should I just return them and get the crucial sticks?
Thank you for your help so far.