Nope, both will work.I am not sure if the hyphen vs slash is making a difference in the syntax.
If the 'Powercfg -lastwake' doesn't give a result, try 'Powercfg -requests' and also do 'powercfg -energy' and have a look at the created 'energy-report.html'. You need to copy if from C:\Windows\System32 to another folder to be able to open it.
Windows 10 seems indeed a bit tricky concerning Standby, i'm also investigating some issues on my DEV PC, although the HTPC goes into S3 just fine with the PowerScheduler plugin.