There is a good practice in OSM called One feature, one OSM element.

https://wiki.openstreetmap.org/wiki/One_feature,_one_OSM_element

Imagine I'd like to gather data on how many museums there are in Estonia. This one museum would count as 2. Or I'd use some phone app to get information about this museum and select this building since it's marked as a museum. It would have no information, since everything is on a separate node.

I'd removed tourism=museum from the building. 

Also, in my opinion, the separate museum node could be moved on top of the building, since I assume this is the place from which you start your visit and where you'd like to be navigated to. Or make it an area which would include the building.