The author states they're using nushell's `markdown` table style because of issues with their font rendering certain characters. `rounded` is the default and indeed, `markdown` looks truly horrible in comparison.
Nushell's front page [1] shows an example of rounded, and here's an example of an even further customized version [2].
I think these are very readable. There is alignment too, but it's "local" alignment to cells in the same sub-table, not "global" to the entire table -- this is good for fitting more stuff into your terminal width without wrapping.
A supporting font is required though, yes.