[MC-236723] The Floating Islands preset does not seem to be generating correctly

The preset for Floating Islands worlds appears to be broken, spawning the player above void, and with terrain features like grass missing. Structures such as villages and pillager outposts spawn at y = -63, and mineshafts only generate below the broken remains of islands.

Game output

15:13:19.150
Empty height range: [6 above bottom--1 absolute]
15:13:19.170
Empty height range: [6 above bottom--1 absolute]
15:13:19.170
Empty height range: [6 above bottom--1 absolute]
15:13:19.170
Empty height range: [6 above bottom--1 absolute]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]
15:13:19.170
Empty height range: [136 absolute-0 below top]