Here is the original paper from the researchers:

https://www.science.org/doi/10.1126/sciadv.ads2426

Apparently they wanted to create a material that:

1. is transparent,

2. can be made thick enough,

3. and is purely cellulose-based.

Cellophane meets 1 and 3 but is hard to be made thick. Paper satisfies 2 and 3 but is not transparent. Celluroid is not explicitly mentioned in the paper, but I gather it does not satisfy 3 since it's hardly pure-cellulose.

The main application target seems to be food packaging.