There are plenty of chapels and crypts filled with bone/skull walls throughout catholic Europe, the author makes it look like this is quite unique and limited to three locations which is not entirely true.
Excuse me sir, but now you're making it look like they are ubiquitous. Pretty sure that's not the case either. So I appreciate this post, first time I hear of this.
EDIT: and in Portugal https://www.ancient-origins.net/ancient-places-europe/story-...
And in Czech Republic: https://en.wikipedia.org/wiki/Sedlec_Ossuary
And in Peru: https://en.wikipedia.org/wiki/Basilica_and_Convent_of_San_Fr...
And another list with 40 entries: https://www.atlasobscura.com/lists/definitive-guide-to-ossua...