As pointed out elsewhere, you are wrong because UTF-16 'characters' can still be comprised of compounded elements. (Base character plus additional composition elements to create a final character.)

In simple terms, you can't just treat it as an array to index to any given character.

There's also all the detriments that still apply. (Including UTF-16LE / UTF-16BE, BOM, not being able to concatenate two valid string sequences (blind) and always have a valid result, etc.)

You're also incorrect, or at least not correctly describing the search operation.

The assumption about finding specific characters (for example, command flags) in a string or array of strings is also... complicated.

As an example: https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms

For /command/ flags the half and full width equivalent characters might want to be 'folded' back over the traditional ASCII namespace.

Sometimes a specific loss of precision can be desirable.