You’re correct, unfortunately clip isn’t preserving the CSRNDArray. Feel free to create an issue https://github.com/apache/incubator-mxnet/issues if you’d like to see this functionality or if you’d like to contribute.
I feel the documentation is generally more in line with the spirit of the data type (not sure about the row_sparse -> default case). I can’t think of a reason why clip should change the data type. In that sense it looks like a bug. I’ll create an issue for this.