In the creative inventory, the potion of the turtle master is missing. Where it should be under the potion droplists is a Slowness 4 potion - however, this potion is missing the name and the Resistance effect. It is still possible to brew this potion using the standard recipe and you will receive the correct potion, but you simply can't get it through the creative inventory. The attached video shows this problem.

I am not aware if this affects other Bedrock platforms, since I couldn't find any other bug reports, so comments would be appreciated if your platform has this issue as well! I play on Switch.