The remarkable speed of the B61-13’s production is a testament to the ingenuity of our scientists and engineers and the urgency we face to fortify deterrence in a volatile new age

ah, the amazing ingenuity of... WW2-era bomb technology? (although it seems like they're also supposed to have guide kits, so they're somewhat more advanced)

Anyway, this seems to be more of a specialized bunker-buster (or more generally a bomb meant for hitting particular hardened bases/facilities and the like, not necessarily fully-underground ones), which is a somewhat different use-case compared to regular nukes - these do need to be gravity bombs as they have to be ridiculously heavy in order to be able to reach the necessary depth of penetration, which makes it not really viable to deliver them by missile.

And it also seems like they'll be a pretty limited production run, and of doubtful utility: https://fas.org/publication/biden-administration-to-build-a-new-nuclear-bomb/

Defense officials explain that the new B61-13 will not result in an increase of the overall number of warheads in the stockpile. The reason is that the administration plans to reduce the number of B61-12s produced by the number of B61-13s produced, so the total number of new bombs will ultimately be the same.

it seems likely that the number of B61-13 bombs to be produced is very limited – perhaps on the order of 50 weapons – and that production will happen at the back end of the B61-12 schedule in 2025.

The military justification for adding the B61-13 to the stockpile is hard to see. Instead, it seems more likely to be a political maneuver to finally get rid of the B83-1. ... The military doesn’t need an additional, more powerful gravity bomb. In fact, Air Force officials privately say the military mission of nuclear gravity bombs is decreasing in importance because of the risk of putting bombers and their pilots in harm’s way over heavily defended targets – particularly as long-range missiles are becoming more capable.

To that end, the military mission of the B61-13 is somewhat of a mystery, especially given that the LRSO will also be arming the bombers and that the United States has thousands of other high-yield weapons in its arsenal. Instead, what appears to have happened is this: after defense hardliners blocked the administration’s plans to retire the B83-1, the administration likely agreed to retain the B61-7 yield in the stockpile in the form of a modern bomb modification (B61-13) that is easier and cheaper to maintain, so that they can finally proceed with the retirement of the B83-1.