Old houses are full of stuff announcing heterosexuality- old family portraits, wedding dresses, engagement and wedding rings, old documents regarding paternity etc. Marriage/having children was hugely significant in the issue of managing large country houses.
I am straight and before equal marriage was implicitly announcing my heterosexuality to loads of people I met , without ever discussing my sex life. The changes in legislation in the last 50 years is massive social history.
The focus on this man is very much because at an early age, when his younger brother died in the war, realised, as he was gay, he was never going to have children so made plans to bequeath the house and contents to the NT. It is great that people are made to understand that gay people are and were everywhere, not just in the arts or London.