The difference is that a typical asset allocation strategy in a target-date fund isn't going to suddenly fall 85% and leave you with 15% of any promised benefit

The difference is that a typical asset allocation strategy in a target-date fund isn't going to suddenly fall 85% and leave you with 15% of any promised benefits, whereas the 1963 Studebaker bankruptcy did exactly that to its employees. (If you're about to retire, it will have at least half of its assets in bonds.) This risk is why Congress passed ERISA and created the PBGC, which nevertheless is at risk of failure itself, with its own projection for its insolvency being about 5 years out.