Hi,
I am not an expert, but that is what it looks like to me.
Masked Language Modelling is usually used during pre-training, and is often not needed during fine-tuning, so I guess the DIMS team didn’t think the MLM parameters would be required.
I notice that the DIMS team have provided 5 models.  Do any of the other models have MLM parameters?
It should certainly be possible to copy the DIMS weights into your own model, where your own model does include an MLM head.  I expect you would then need to train your model before it would give sensible answers, unless you could find a suitable MLM head to copy (probably not…).