Has VISIBILITY property become case-sensitive?

[Richard Stanton]

My org file has the header line 

#+STARTUP: overview

One section contains the properties drawer

:PROPERTIES:
:Visibility: content
:END:

This used to show the contents of that subtree on first loading the file, but 
it no longer does. Experimentation shows that it works if I change “Visibility” 
to “VISIBILITY”. Is it a deliberate change to require upper case here? By the 
way, this is using org version 9.7pre

Best,

Richard Stanton