ASCII just refers to the 7bit standard, so if we are pedantic ASCII art is just art using the printable characters of the 128 code points defined in it. Font size doesn't have anything to do with it. But ASCII art is used as an umbrella term, encompassing a variety of different standards, character sets and fonts. There are a bunch of square ASCII, like PETSCII, ATASCII and even PC ASCII can be rendered with a 8x8 cp437 font. We don't need to gatekeep what "qualifies" as ASCII art.
Self plug: the “ASCII Playground“ has a couple of 3D demos as well!
DOM manipulation is fast enough to allow text output into a PRE element as long as text color is not changed too often (each style change needs the affected chars wrapped into a SPAN).
Would have expected something more sophisticated, where the shader also looks at subpixels, where it gets the best matching char for the shape and brightness.
Like rastapasta map renderer did with the braille block:
https://threejs.org/examples/?q=asc#webgl_effects_ascii