I have tried the wuauclt
/reportnow command before and it does not seem to be doing anything that actually speeds up client reporting.
It looks like they still report whenever they get around to reporting and running the command doesn't make it faster.
The /reportnow function is a very tricky beast, and it somewhat requires an understanding of the natural behaviors of the WUAgent.
When the WUAgent performs activities, it queues up all of those completed activities as 'events'. When the WUAgent quits working, an idle timer is engaged, and when the WUAgent has been idle for ~20 minutes, it invokes a call to the ReportingWebService.
You can see these calls in the WindowsUpdate.log and compare their timestamps with the entries just previous.
If the /reportnow action is invoked after the WUAgent becomes idle and
before the regular call to the ReportingWebService, an immediate call to the ReportingWebService will be invoked. You can also see this in the WindowsUpdate.log.
However, the call to the ReportingWebService is not the end of the line. Those events reported in that call are loaded into a buffer, and the WSUS server then processes those events asynchronously. If the WSUS server is also busy doing other things or other
clients are also reporting at the same time, there will be an additional delay until the results are visible in the WSUS console.
The real thing to remember is that, at best, the /reportnow task isn't going to save you much more than 20-30 minutes, so usually just waiting is the more efficient approach to the whole thing.