Bonus chest loot and location is not consistent per seed

If enabled, the bonus chest spawns somewhere close to the world spawn. Recreating the world with the same seed will randomly generate the bonus chest in different locations, and with different loot.

Examples of chest locations:

And loot:

The bonus chest location and loot should be consistent per seed, like all other generated structures and their chest loot.

This issue has been present from at least version 1.14 (or earlier), but for example 1.8 still had consistent bonus chests.