Eat And Eat

The halacha is that the korban pesach must be eaten על השובע, when one is already satiated.  This din according to Rashi (86a ד"ה אין מפטירין) applies to all korbanot and is learnt from למשחה, that kodshim must be eaten just as kings eat. In his words, שכן חובת כל הקרבנות כדקיימא לן למשחה לגדולה כדרך שהמלכים אוכלין. 

However, the Mechilta says על מצות ומרורים יאכלוהו" (במדבר ט, יא), מכאן אמרו: הפסח נאכל אכילת שבע, ואין מצה ומרור נאכלים אכילת שבע.  According to the Mechilta it is a din specific to the pesach that it must be eaten על השובע.  However, what is wrong with the general din of למשחה, why does the Mechilta feel the need to come up with a different source?    The Rambam (Korban Pesach 8:3) says that the chagigah is eaten before the pesach so that the pesach will be eaten על השובע.  In other words, the din of על השובע is only a din in korban pesach.  The source of the Rambam is a berasah in Pesachim (70a) and it is צ"ע according to Rashi what is the reasoning of the berasah that the chagigah is eaten first so that the pesach shall be eaten על השובע if the chagigah has the same din?    

The Rambam perush hamishna Zevachim (10:7) says אמר רחמנא בדברים שהכהן אוכל למשחה.  He holds that למשחה only applies to parts of a korban that the kohan eats.  In light of this Rambam we can understand that there would be no din of למשחה for korban pesach since it is a korban that non-kohanim eat.  (One may understand the Rambam may be lishitaso that the mitzvah of eating kodshim is only on the portion that the kohan eats, see Briskor Rav Menachot 21b., in which case, pesach in which there is a mitzvah to eat it would have the din of למשחה.)  That may be why the Mechilta needs a new limud to tell us that the pesach has to be eaten על השובע (Briskor Rav.)  

Tosfot Pesachim (70a) cites from the Yerushalmi a different reason why the pesach is eaten על השובע and that is so that won't be ravenous and come to break a bone of the pesach.  Why is the Yerushalmi not satisfied with the with the reason of the Bavli so that the pesach is eaten על השובע?  It is possible that the Yerushalmi holds that למשחה doesn't apply on non-kohan portions and does not hold of the derash of the Mechilta and therefore needs a Rabbinic reason to explain why the pesach must be eaten על השובע. 

The Mordechai (end of Pesachim) says the Yerushalmi was bothered by the question we asked on Rashi.  Why put the chagigah before the pesach so that the pesach is eaten על השובע if the chagigah has the same din?  Therefore, the Yerushalmi enters a new reason as to why it is important for the pesach to come after the chagigah.