I’m confused about what you are trying to do and why. If I knew more about the final result and the need, I may be able to suggest a better way to go about this.
Do you need to get this result from all computers, or just specific computers?
It might be better to start with an automatic group that filters to just the computers you need to get these results from, then query the computers of that automatic group.
Part of your issue is that bes computers is going to examine EVERY computer even when not required.
What is bes property "Site" and does it relate to Custom Sites within BigFix, or this is physical locations/offices?