In the end, I did not open a support case. When I discovered this, we were in the final planning to perform a migration from RHEL7 to 8 and application upgrade 10.0.3 to 10.0.7 and I elected to wait until after to reassess (if the issue persisted).
The migration (Dec 15) did not have any impact to the import duration as one additional import ran that night on the new OS and VMs and still took ~6 hours.
After the upgrade, the imports dropped to the ~15 minute range. Sometimes under 12 minutes.
Wed, 14 Dec 2022 11:33:56 -0500 -- Beginning DB import of version 4108 of site Enterprise Security
Wed, 14 Dec 2022 17:45:32 -0500 -- Import of version 4108 of site Enterprise Security completed successfully
Wed, 14 Dec 2022 18:46:10 -0500 -- Beginning DB import of version 4109 of site Enterprise Security
Thu, 15 Dec 2022 00:58:28 -0500 -- Import of version 4109 of site Enterprise Security completed successfully
**Migration RHEL7 - RHEL8**
Thu, 15 Dec 2022 18:25:44 -0500 -- Beginning DB import of version 4111 of site Enterprise Security
Fri, 16 Dec 2022 00:25:05 -0500 -- Import of version 4111 of site Enterprise Security completed successfully
**Upgrade 10.0.3 - 10.0.7**
Mon, 19 Dec 2022 13:17:07 -0500 -- Beginning DB import of version 4112 of site Enterprise Security
Mon, 19 Dec 2022 13:32:16 -0500 -- Import of version 4112 of site Enterprise Security completed successfully
Tue, 20 Dec 2022 16:08:11 -0500 -- Beginning DB import of version 4113 of site Enterprise Security
Tue, 20 Dec 2022 16:22:02 -0500 -- Import of version 4113 of site Enterprise Security completed successfully
Not exactly clear what the cause was, but happy to say it seems to have been resolved by upgrading and grateful for one less case to wrangle at the start of the year!