Howdy! Nice job on this switcheroo on the church grounds/buildings. In the past I've typically tried to put most everything on the grounds/landuse, leaving a generic building=church within, but I just had a skim of the wiki for amenity=place_of_worship and it looks like the way you've done it is the more accepted way. I'll try and remember this for when I next touch a church building/grounds. In the past my main goal has just been to avoid amenity appearing on multiple features which is a duplicate afaik.
TL;DR nice job. :)