A rebellion is against the government, not against the land owners (lords and dukes).
well, the whole idea is about changing that a little.
currently, as there is tendency for realm council weakening, that together with the fact how easy it is to stay intact by rebellion, even when actively supporting one party makes rebellion rather sterilized, and even more creates one of problems which is present in other aspects of the game - those who risk the most are not likely to gain anything, those who risk little or nothing are likely to preserve their posts.
what power rebellion currently can gain in anyhow powerless council? at most, in respect of this discussion, position of judge who could eventually ban someone.
however, even that is very limited - new ruler who remains in throne will have the same structure as before, and let us say if judge was neutral during rebellion, he can retain such neutrality afterwards as well, which hypothetically means that even if rulers gains enough supporters and win rebellion, loyalists can be unable to even punish rebels, which is rather awkard if we consider that all is at stake for those who take part in rebellion.
if rebels win, new leader will hardly be able to appoint himself as a judge if he does not want to look as tyrant. and he can appoint someobody else and that push new judge to ban nobles he dislikes. again if such nobles held formal neutrality, that looks as dictatorial act.
so winning rebel can very likely have two choices, both being bad - to either look as heavy tyrant at very beginning of new career or to retain all power structures as they are. that means rebellion gives very little in any case.
if claims would be disputed in way, that winner of rebellion has option to dispute or reconfirm claims, as a formal act not related to any other aspects of law system, that could give him option to really change something. than he is not automatically tyrant, but he uses his discretion one-time-only right to deal with claims.
i cannot be certain, but i believe some background ould be found for it.
feuds cannot be looked at something completely isolated from anything else. if rebellion has power of changing complete structure of the government, why it should not have power to question claims?
ducal oaths belong to ruler and if we say that in regular elections new ruler automatically recognizes all previous claims as he participates in official and regular election, the same way we can say that rebellion acts against regular hierarchy in general.
these are thoughts only, of course. the main idea is that rebellion becomes real thrill for all with significant power. current position where many in power simply remain neutral like "that is not our business, we will be safe anyhow" is rather unnatural.