It's nothing to do with which object is selected, it's just the amount of information being displayed in the tables. The system tab does show a lot of information!
I did some testing just for fun and done know if it useful in anyway. But I added all the system information to the watch.
There are 9 layers.
And this is what it shows:
It jumps between 25% to around 40% CPU
So I tried removing "Time", "Wall clock time" and "Tick count" from the watch and this is what I got.
Here it jumps between 0 and 4%
Another test, if I leave everything on watch, but remove all the things in "Performance" except "Est. CPU untilisation" and "Frames per second" this is what I get:
And it will jump between 17% to around 23%
But if I remove either "Est. Cpu utilisation" or "Frames per second" not both of them but just one. then I get this:
And it will jump around 54% to 60% which is a bit weird.
If I remove the "Time", "Wall clock time" and "Tick count" as well then I get this:
And it will stay at a solid 0%.
Anyway not sure its useful, but it seems that depending on what stuff it is told to keep track of, will lead to significant different results, which ofc makes sense. But if the data it gives you varies so much depending on this, then the information it provide is not really reflecting the performance of your game, but rather that of the web browser, if I understood you correct?. And think that would be a bit sad, if that's the case.