You don't expect to get a confirmation for using non-Fujitsu memory modules in a Fujitsu server board here, do you?
Generally, the speed value noted in the module's product name is nothing but a maximum value. The child needs a name, you know. The modules also do work perfectly well at lower speeds. Depending on CPU (i.e. memory controller) and board design, even using more than one single module on a memory channel already decreases the actual speed getting selected.
It all depends on the timing information sets stored in the module's identification chip, to match with the possible parameters that the initialisation routine in the mainboard's BIOS (or UEFI) offers.