They need to take into account that their survey is horribly skewed. That is, it was only presented to people who had even heard of Nushell and were in the right place and right time to participate.
I strongly suspect that their ~50/50 split is closer to 90/10, where 10 is their usage compared to bash, fish, zsh and whatever else is in use these days.
(An interesting comparison might be between the number of Nushell users versus the number of current (t)csh users. Nushell might win that one.)
Note that this isn't a criticism of how well (or not) Nushell works. I don't know enough about it to make that judgement, and definitely haven't used it. Until this post I hadn't heard of it (or had but then forgot it), which is why this comment exists in the first place.
I don't think they're interpreting that question as a gauge of how widely used nushell is in general. The comment below the result seems to be about how they should interpret the rest of the survey based on the ratio of users to non-users who responded.
I think what nushell needs is a side by side comparison of some operations in other shells. At the moment, I have no idea what it would do to my system if I made nushell my default shell.
It doesn't really do anything to your system. nushell focuses on working on structured data as opposed to raw text. It's very cool though it does have some shortcomings here and there that make it impractical.