I have a small world that I thought would be fun to make infinite and get all the cool 1.18 features! But was disappointed to find out that the height didn't change nor did the bedrock at the bottom get removed. As mentioned in the summary I did have experimental toggled on and I am not sure if that effects the outcome of making a world infinite including the features. As I don't have another small world to experiment with unfortunately.
Thank you for your report!
We're tracking this issue in MCPE-149233, so this ticket is being resolved and linked as a duplicate.
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