buffers not supported?

I got a report that ipyvolume does not work on colab at https://github.com/widgetti/ipyvolume/issues/436

I eventually traced back part of the problem that the buffers at:
https://github.com/googlecolab/colab-cdn-widget-manager/blob/664b13da3289597966bfb5b7dd5e347233d48524/src/manager.ts#L222
Are not being used.

I think this is a bug.