the avos feel pain after death

In this week’s parsha, the Jewish people request permission from the King of Edom to pass through his territory and make the case that although they descend from the same family the Jewish people alone bore the burden of Egyptian slavery, so in effect, they owe us one. Commenting on “Vayare’u lanu v’la’avoseinu” (20:15) Rashi explains that the deceased Avos feel pain when their children are persecuted. I have not had a chance to check the meforshei Rashi yet, but the point here seems hard to fit with Brachos 18b. The gemara describes how R’ Chiya’s sons were in grief because they forgot their learning and debated back and forth whether their deceased father was aware of their pain or not. Is it only the Avos which suffer when their children feel pain? Is it only the pain of persecution (like Egyptian slavery) which is felt, but the gemara was unsure whether it extended to other grief that children may suffer? Other possibilities?