What is the exact meaning of the new "last checked" date info on EUTL Source of Trust message, that is appearing in newest Reader versions (2026.001.21662+)

Product: Adobe Acrobat Reader (Continuous track)
Versions observed: 2026.001.21662 → 2026.001.21677 (English UI)

Description:

Starting with version 2026.001.21662, the signature/seal validation panel shows an additional date appended to the existing trust-source message:

Source of Trust obtained from EU Trusted List last checked on 2026-06-05

In prior versions, this message did not include a date — it simply stated that trust was obtained from the EU Trusted List (EUTL).

Testing performed:

1. Verified two independent qualified signatures/seals, based on certificates issued under different national Trusted Lists:
   • Czech Republic (CZ)
   • Belgium (BE)
   Both show the identical date: 2026-06-05.
2. Compared this date against official EU trust-list metadata:
   • EU LOTL (https://ec.europa.eu/tools/lotl/eu-lotl.xml) — ListIssueDateTime: 22 May 2026; NextUpdate: 18 Nov 2026.
   • Czech national TL (https://tsl.gov.cz/publ/TSL_CZ.xtsl) — issue date: 16 June 2026.
   Neither matches 2026-06-05.
3. Performed a manual trust-list refresh via Edit > Preferences > Trust Manager > Load trusted certificates from an Adobe EUTL server > Update Now. The "last checked" date did not change.
4. Upgraded the application from 2026.001.21662 to 2026.001.21677 (released 2026-06-17). The date still shows 2026-06-05, unchanged.

Question:

What does this date actually represent? Candidates considered and apparently ruled out by the above tests:

• It is not the ListIssueDateTime of the EU LOTL.
• It is not the issue date of the relevant national Trusted List.
• It does not reflect a live/manual "Update Now" check (date unchanged after refresh).
• It does not appear tied 1:1 to the installed product build (date unchanged across two subsequent releases).

The most likely remaining explanation is that this date reflects when Adobe's own internal EUTL bundle (the subset of LOTL data Adobe redistributes to Acrobat/Reader) was last regenerated/published on Adobe's side — independent of both the official LOTL update cycle and the Acrobat/Reader release cycle. Could Adobe confirm:

a) The exact meaning/source of this timestamp, and
b) Whether there is (or will be) documentation describing this new UI element, including the build in which it was introduced.