Does the queued activity require some parameters taken from the step page? That is, when you expand the method parameters, do you see any parameters that are clearly referring to the step or primary page? If you do, it won't work because for the reason stated in the guardrail warning. Perhaps if you remove such a reference (do you have one?), the warning will go away.
We do have some parameters to the Queue activity but there is no dependency on any Primary page or Step Page reference. These are just some string parameters where we pass some hard coded values. I also tried calling an activity with no parameters at all, but I still see the same severe guardrail warning.
I spoke to my team, and the suggestion was to fill in the "justify" field in the warning. You can just say "there is no problem here " (or anything else you wish) and that should remove the warning from your score.