I couldn't easily lay my hands on my EFDSS PLI documents so I googled and came across a dccument "English Folk Dance & Song Society's Public Liability Insurance, Basic principles for Members and Affiliated Groups". Strangely, I couldn't find this on EFDSS's own website and they don't seem to have done much to draw it to members' attention, but you can find it here:

Leicestershire and Rutland Folk

It makes a clear distinction between individual cover (which covers only that person's activities, and not any events which he/she may organise because that inevitably involves other people), and group membership which covers only the group's activities and not those of individual members.

As an organiser of Poynton Ceilidhs we have group membership which covers the ceilidhs, but if I and the other organisers perform there as musicians we are not covered and need separate PLI (which our band has).

I suspect this would apply to most PLI policies, unless you had made it clear that you wanted cover both as a performer and as a promoter, in which case it would be reflected in the premium. As I said in my previous post, they are different roles and each require their own PLI.