Oracle's system largely does nothing for you, it's just an entry system (and horrid to work with as an end-user/worker). It's mostly just a way to [mis]represent what you've done according to accounting categorizations that have little to do with how you would usefully categorize your own work for your own line managers. The main virtue (if you can call it that) is that it feeds directly into the wider accounting system.

For goverment contracting, I'm guessing it just enforces rules about when you can enter your time (daily), and a process for revisions. That's largely out of scope for ManicTime. It need not be the "system of record" for it to be useful to individuals or teams.

I used ManicTime (with permission) on my local systems, then used it to make reports for myself to present the relevant information demanded by the project/task breakdowns created within the Oracle system by higher level management (billing codes, etc). The work is in creating a parallel tagging taxonomy within ManicTime, and generating reports based on those. That was not easy, since what I cared about tracking, to know what I had actually done for reporting my progress, was not the same kind of thing that the Oracle breakdown was demanding.

The internal Oracle web site was SSO enabled, so you would just access it from your desktop without separate login (thank god for small favors). This (among other things) necessitated a corporate screen saver policy to prevent entry by anyone other than the user themselves. The same policy would cover your use of ManicTime.