Quotes from OSM wiki on bay..

Bays are frequently mapped as nodes, and rarely as areas.

Large bays can be mapped as areas but the resulting multipolygon relations will often be extremely large and complex so mapping with nodes is preferable

End quotes... 
Some 56,450 mapped as nodes .. some 3,563 mapped as ways (assume fjords) and some 20,377 as relations. So a little over 70% are mapped as nodes, I'd think that is fairly 'frequent'? 

I note that neither of the 2 relations given as example look to render while this does render 
https://www.openstreetmap.org/node/3963720669

