Thanks - yes, UTC occurred to me, but I didn't understand that SWIS was adjusting values to UTC even when they were server local to begin with - however, this only makes sense with the SWQL query if 'getdate' is returning local server in server time with no adjustment, leading to my MinuteDiff taking four hours and thirty minutes instead of thirty minutes. I believe I have fixed the query with 'getUTCdate' - however, to account for the differences between the SWQL Studio and the Custom Query, it seems that 'getdate' would have to be pulling as UTC for Studio (resulting in correct results, but +4) but on Orion Custom Query pulling local server time for 'getdate' while still be doing +4 on the values from Orion.CPULoad.DateTime.
If there were no difference between SWQL Studio and the Custom Query, then the results certainly should have matched, regardless of the timezone formatting.