First, I think it's really important to treat Altair as just one of many contributors to the PBS Pro Open
Source Project, so Altair should not get any special treatment for "internal" use cases. We should always be focused on making PBS Pro better for the the whole community.
Historically, the accounting records have primarily been used for extracting resource use data for billing (charge-back, reporting, allocations, etc). Originally, this only meant "resources actually consumed by jobs", but now includes the lost opportunity costs of resources not available for other jobs (e.g., a reservation may prevent some jobs from starting, which is an opportunity cost that some sites want to consider in billing and reporting). Having a full workload trace (not only what is consumed, but also what is requested, and when) is really important for determining opportunity costs. Further, a secondary use of the accounting records is for debugging, troubleshooting, and simulation -- and for these use cases, getting the full workload trace is required (and there are multiple sites who use accounting logs for this secondary purpose, including Altair).
Note: the daemons logs are not a good substitute for capturing this data, as it is common for sites to keep only a few months (or days) of daemon logs, but sites generally keep accounting logs indefinitely. (Plus, the accounting logs tend to be a more stable interface.)
If it makes more sense to add it to the U records (instead of the Y record), that's fine. I suggest checking with @agrawalravi90 who filed PP-703 to understand more deeply what needs to be captured (or what is not already captured today).