In Keilim 12:8, we see that unfinished wooden utensils with a receptacle are susceptible to tumah, except those woods whose properties make the utensil unusable.
... כל גולמי כלי עץ טמאין, חוץ משל אשכרוע. רבי יהודה אומר, אף גרופייות של זית, טהורה, עד שתישלק.
... All unfinished wooden vessels also are susceptible to impurity, excepting those made of boxwood. Rabbi Judah says: one made of an olive-tree branch is also clean unless it was first heated.
However, in Keilim 12:6, we have a disagreement as to whether unfinished metal utensils are susceptible to tumah.
ארבעה דברים רבן גמליאל מטמא, וחכמים מטהרין... וגולמי כלי מתכות...
There are four things which Rabban Gamliel says are susceptible to impurity, and the sages say are not susceptible to impurity: ... and metal vessels which are still unfinished ...
Although Rabban Gamliel's opinion in 12:6 works well with 12:8, the sages' opinion does not. What are ways that commentators have tried to resolve this?