There is a small extra cognitive shift where the brain realizes those aren’t typos or random letters and are intended to represent those words, so it does add an impediment to understanding. If it became common for people to write them as ‘r’ and ‘u’ then over time that would become correct.
Just like if it was common for people to pronounce “gif” one way and then someone came along and said “Well the creator wants it pronounced another way” the correct response is “who gives a fuck? This is how the word is used now.” The ‘creator’ of the word “island” did not have an ‘s’ in it, but no one is arguing for it to be spelled “eyland”.