I agree with you if you need to impute missing data, anything you can hang on a hat would help. For the ETLer that may be something to think about. But for the analyst? That poor wretch has no chance to tweak individual patients. Phenotyping is hard enough the way it is using the data at face value.
If you have a use case of using this type of information for an analytic those flavors of null could be back in business.