Despite being an overworld wood set, shipwrecks aren't able to generate with mangrove wood.
Can be reproduced by /locating multiple shipwrecks, and then noticing that none of them have mangrove blocks.
There are also no entries for the mangrove blocks in the shipwreck NBT files.
Can confirm. Every other overworld wood type has a shipwreck version besides acacia, which itself is a parity issue with Bedrock as Bedrock can have acacia shipwrecks.