The Staging Environment web page is now updated with details about the new Staging Root and Intermediate.
In the next few days and weeks we'll be making more changes to the Staging Environment so it will better match Production and offer a useful test environment for upcoming production changes like the chain switch and signing from our ECDSA roots and intermediates (noted as 'upcoming').
Addtionally, we noticed our test hierarchy has the wrong AIA CA Issuers URI and CRL Distribution Point URI on the certificate: (STAGING) Artificial Apricot R3 signed by (STAGING) Doctored Durian Root CA X3. That fix will be done in the next few days too.