That is unfortunate. Also, as custom dimensions are a experimental feature, it probably isn't on the top of their list of things to fix.
Additionally, I suspect that what is happening is that the world is optimized upon upload, and it doesn't recognize the custom dimensions as being needed. I may do some further research in the near future, and think it may be possible to work around this, though I can't say for sure
That is unfortunate. Also, as custom dimensions are a experimental feature, it probably isn't on the top of their list of things to fix.
Additionally, I suspect that what is happening is that the world is optimized upon upload, and it doesn't recognize the custom dimensions as being needed. I may do some further research in the near future, and think it may be possible to work around this, though I can't say for sure