Since the Nether update the world generation on Bedrock servers generates stone instead of biomes in all chunks in new and pre-update worlds. However the generation in a local world is not affected perhaps it is a mistake of the Bedrock server generation.
ps: it happens in both pocket edition and Windows 10 version
Thank you for your report!
We're actually already tracking this issue at BDS-6230, so I will resolve and link this ticket as a duplicate.
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