I would expect all surface-type Buffet worlds to generate ocean monuments in valid deep ocean biome locations. However, when the NBT generatorOptions tag is set to use multiple biomes, such as with the "checkerboard" option, then ocean monuments will only generate if all specified biomes in the biome list are variants of a deep ocean.

E.g. the buffet option:

{"biome_source":{"type":"minecraft:checkerboard","options":{"biomes":["minecraft:ocean","minecraft:deep_frozen_ocean","minecraft:deep_cold_ocean","minecraft:deep_warm_ocean"],"size":4}},"chunk_generator":{"type":"minecraft:surface","options":{"default_block":"minecraft:stone","default_fluid":"minecraft:water"}}}

will not generate ocean monuments (can be checked with /locate Monument). However, monuments will generate when "minecraft:ocean" is removed or replaced by "minecraft:deep_ocean":

{"biome_source":{"type":"minecraft:checkerboard","options":{"biomes":["minecraft:deep_ocean","minecraft:deep_frozen_ocean","minecraft:deep_cold_ocean","minecraft:deep_warm_ocean"],"size":4}},"chunk_generator":{"type":"minecraft:surface","options":{"default_block":"minecraft:stone","default_fluid":"minecraft:water"}}}

 
I have attached a zip of two worlds which consist both of only their level.dat files. The two files are identical, except for the generatorOptions, which are those shown above. I chose a seed that should generate 4 ocean monuments very close to spawn / the origin.

As a side note, this behaviour does not appear to affect biome dependent scattered features such as swamp huts.