When a mangrove swamp biome generates near sea a beach will always generate separating it from the ocean. However that's not how mangroves work in real life as they're transitional biomes from the sea to the land, so it would make more sense for them to directly border the ocean without a beach in between.
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The 22w14a changelog states that mangrove swamps are:
Located in warmer, more humid places where you’d normally find the Swamp biome in Minecraft
I'm not sure whether beaches are considered "warm" biomes or not, but this type of generation seems intentional to me, although I can confirm this, nonetheless.
sounds like a feature request to me
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