I asked the same question within a support ticket. Here is the verbatim response related to that:
it is compatible only with WD reds and green’s, both drives placed need to have the same model and capacity.
we recommend to Only use WD Red™ or WD Green™ hard drives to replace the drives in your My Book Duo device enclosure. Also, replacement drives must be new, and the same capacity as the drive that failed.
p.s. if you have the chance to test it with other drives, like the one you mentioned, would be great to read how it went.
pps. however, I recommend you stop using this particular product due to the “hardware encryption”, which you can’t get rid of and you put your data at risk due to that and store/secure your data on another “USB product”, which does not come with this “feature”. You may want to have a look at my made bad experience with the MyBook Duo: here
