See, I think just the opposite. To me, the two hammer strokes don't signify so much an end to something, but rather the beginning of a huge cataclysm. It's like huge amounts of water pushing against a dam that can no longer hold back the mounting pressure. In this regard, the sixth Mahler makes me think of Stravinsky's "Rite Of "Spring" - an unleashing of vasts amounts of energy. In fact, combine the huge walls of sound from the finale, with the continuous mixed meters that happen in each of the trio sections from the scherzo movement (constant interchange between 2 and 3 beat patterns), and you'll get - voila!!! - "Le Sacre du Printemps". No doubt, though, that the imagined protagonist of the symphony gets caught up in these whirlpools - or vortexes - of violent energy.
Just to be clear what happens at the hammerstrokes, in the revised version - the one that's ALWAYS performed - both strokes are doubled with the bass drum. Mahler specifies that the hammerstroke itself be of a non-metallic material and sound. The second hammerstroke calls for OPTIONAL doubling with the cymbals and tam-tam (along with the bass drum). On most recordings, you'll hear the cymbal and tam-tam added to the second crash. Weirdly enough, Abbado seems to have added the tam-tam on the first hammerstroke as well, on his latest Berlin remake from DG. The third stroke is not indicated as being an option in the revised version.
Therefore, when conductors reinstate the third stroke, they're doing so on their own accord. The orchestration surrounding the third stroke is a bit different in the original, first version. Zander tried to make that point, but he failed to use the first version throughout the finale on his second performance of it (included on the second disc). That made the claims of an "original version" on the cover, something of a false statement (and thus, false advertising).
For my money, the best hammer strokes - as well as cowbells - are on the Chailly/RCOA recording. However, the Concertgebouw no longer use the optional doublings on the second stroke (in other words, they didn't on the Jansons recording either). Chailly was a percussionist first, and takes great care with his percussion parts when conducting (for the most part).