It is highly annoying that you cannot check the type of properties in python scripts. The only way I found is to write a value of dffferent types to the property, check if this is succesful and catch the error if it fails. However, writing to a table or column property can lead to reloading of data, so this method is not a good option in all cases.
So, I think the DataType of the properties should really be exposed in the API.
I had a look again. My request is not necessary. You can easily type-check the document Properties using something like 'if type(DocumentProperty) is str' or similar. Exposing the data type in the api is thus not really necessary I think.