> using capital i as roman numeral lookalike (instead of unicode) theirs

At least that much is correct. Quoth the Unicode Standard:

> For most purposes, it is preferable to compose the Roman numerals from sequences of the appropriate Latin letters.

[from https://www.unicode.org/versions/Unicode6.0.0/ch15.pdf]

Note that Unicode has a lot of characters like this — compatibility forms which are present to allow lossless conversion to/from other character sets, but shouldn’t be used in any new text.