www.archives.gov - "Transcript" section is not displayed in reader mode

[sv-calin]

Environment:
Operating system: Windows 10
Firefox version: Firefox 140.0/152/154

Steps to reproduce:

1. Go to https://www.archives.gov/milestone-documents/president-john-f-kennedys-inaugural-address
2. Enable reader mode.
3. Observe the content.

Expected Behavior:
"Transcript" section gets displayed as well.

Actual Behavior:
"Transcript" section is missing in reader mode.

Notes:

• Reproduces regardless of the status of ETP
• Reproduces in firefox-nightly, and firefox-release
• Does not reproduce in chrome

Created from webcompat/web-bugs#227936