Alan Barlow was the co-ordinator when I hosted in 2014. It was still fell then. although people would contest the venue as being fell, but I did talk to him about the purists complaining.
His view (I paraphrase) was that there were other championship events out there for purist fell runners, but when it came to Inters, consideration had to be given to counties with less of a fell pedigree and little ability to recce who might have to co-opt in general endurance runners.
Typically around 20 Mens Counties finished teams and maybe 10+ ladies teams. That could have halved if we tried to send them around a typical AM where NS, ER and particularly LK are advised.