A) The members of Tool that the guys in Motorhead saw and interacted with in the studio were actually the DECOY members of the band , who have started tracking tunes for the new DECOY Tool album.
B) Rather than tracking tunes for the next Tool record, the (real) members of the band have begun tracking (real) tunes for the Tool album that is to be released AFTER the next Tool album is released.
C) Rather than tracking anything, the members of the band were in the studio mixing music that was recorded sometime ago, which might not have anything to do with the next Tool album (which is still in the writing/arranging process), but might be used for another Tool project that has been in the works for a while, of which I am currently not at liberty to add any further details.
D) All of the above.
Seeing as I expect the first two are unlikely, I imagine C is the most likely option. Maybe one day we’ll even get some details on what this actually is!