On older websites (ex: 2018/10), the
GET https://msdn.microsoft.com/en-us/library/office/dn499819.aspx#bk_WebEndpoint and
GET https://msdn.microsoft.com/en-us/library/office/dn531433.aspx#bk_ListEndpoint endpoints always return the Title and Descriptions used to create them, not their current values displayed in the Sharepoint Online UI.
For example, if I create a list called "abcdef" and change its title to "123456", its title is clearly changed in the UI but if I GET it, the returned title is still "abcdef".
However, if I create a few new site collection (2018/12) and try the same thing (change Title -> GET List) on all of them, all of them have the correct (new) titles.
I'm guessing Sharepoint Online updated something that affects sites created after that, but did not push the updates to sites created previously. Can anyone confirm if there was indeed a patch between this October and December that only affects newly created site collections' REST API's behaviors?