I hear your concern and agree that it could be an issue. I'm not sure adding a new option is the answer though. We'd then have two ways to print pretty much the exact same data. I doubt the new option would be used. I removed the new column from interface 3. You can still obtain the arbitrary usage via pbsfs -g for an entity.
The IFL API talks to the server. The fairshare usage is in the control of the scheduler (at least for now). The pbsfs command directly talks to the usage file. So no, we don't need to worry about the API.
PTL is currently broken when it tries to reset the fairshare usage in revert_to_defaults(). It tries to remove the usage file. The file gets rewritten on the next scheduling cycle.
To fix this, I have added interface 4. Right now when the scheduler receives a HUP, it will write out its view of the fairshare usage before rereading it again. This ways needed back when we didn't write out the fairshare usage every scheduling cycle. I will modify this behavior so that it won't write out the usage on a HUP. It will just read the current usage file. If changes were made via pbsfs, the scheduler will see them.
PTL reverts to defaults by removing the fairshare usage file. I'll modify the PTL library to HUP the scheduler after it does so.