See, there is lot more happening in this.
First of all you need to get to know why we use virtual concept here.?
As in major industries, tb designers and test cases designers are two different teams. As that of SV testbenches testcases writer needs to remember the name of the handles, due to which both team has to constantly communicate which was a major drawback.
Here in virtual concept, test case writer just need to know the handle for virtual sequencer, anyway virtual sequencer has the handles for actual sequencer present in the agent.
So, virtual sequence can be started over virtual sequencer, which in turn started over actual sequencer “virtually”.
Hope this helped you to grow
Regards
Ujjwal