The gemara says that if one does the kemitza of a korban mincha inside the heichal, it is kasher because we learn from the bazichin removed from the shulchan every week which is similar to kemitzah of a mincha that it can be done in the heichal. Tosafos asks, why does the gemara have to learn from bazichin rather than just using the same logic used to permit eating kodshim inside the heichal (when goyim surround the azara and make it unaccessible) which is שלא יהא הטפל חמור מן העיקר. Tosafos explains that the sevara of the tafel (courtyard) not be better than the ikar (heichal) only applies to cases where the pasuk explicitly says that it should be eaten פתח אוהל מועד or בחצר אוהל מועד, implying that the right to eat it there is connected to the ohel mo'ed. But when there is no indication that there is a connection to the ohel mo'ed, we don't use that concept.
The gemara 8b asks why we require a special passuk to permit the eating of kodshei kodshim in the heichal when the courtyard is unaccessible - why don't we just use the sevara of שלא יהא הטפל חמור מן העיקר? The gemara answers that this logic would only apply to an avoda but not to eating since eating is inappropriate to do in the presence of the shechina. Rashi explains that when the gemara asked the question it thought that the pasuk is necessary to teach that the p'sul of יוצא would only apply if the kodshei kodshim was transported further out, not closer in to the heichal. The gemara asked that this idea can certainly be derived from the logic of שלא יהא הטפל חמור מן העיקר. Therefore the gemara concludes that the fact that the kodshei kodshim doesn't become pasul when being brought into the heichal is in fact learned from the sevara of שלא יהא טפל חמור מן העיקר, but the right to eat inside the azara which would seem inappropriate to do in the presence of the shechina, requires a special pasuk.
From Rashi's approach we learn that the sevara of שלא יהא הטפל חמור מן העיקר tells us 2 different dinim. 1. avoda that can be done in the courtyard, can be done in the heichal. 2. when there is a p'sul of removing something from the courtyard i.e. יוצא, it wouldn't apply to the heichal. However, the eating of kodshim in the heichal isn't learned from this sevara and requires a pasuk. The Brisker Rav discusses whether the pasuk is mechadesh that it is mutar to eat kodshim in the heichal under extenuating circumstances (rashi) or whether it is to teach that one fulfills the mitzvah of eating kodshim even when it is done in the heichal (rambam).