Even though it runs locally, it is network-connected to the tile server that provides you with the vector tiles (unless they are cached locally after their first use). You currently have to wait for the requested tile(s) to be downloaded, processed, and available in memory before continuing rendering (which is slow in direct comparison to rendering itself). Could be improved by continuing to render the zoomed features of the parent tile until its children are ready (triggering a re-render) - but for now, it simply lets you wait until then :)
Very odd - na, that's a bug and not a feature, I'm just throwing color coded Braille characters at you ;) Most likely related to your Terminal version, http://iterm2.com might help.
Good question indeed, main reason for me was the incredible well toolset in the node.js world around Vector Tile based map data and GIS processing. Check out the list of used libraries in the repo and you might understand ;)