You have to weigh your personal benefit, against the benefit of keeping the company running somewhat smoothly (which is also in your interest). Assuming titles don't affect your current salary/equity in the company (you can get this in writing), it is only your future job prospects that are affected. The CUXO is probably (perhaps rightfully) worried his title sounds too unserious, and wants a better safeguard.
That said, changing the deal you had all agreed to at the start also makes working together harder. Instead of focusing on the company, you find yourselves also fighting among each-other, since the clear lines you had drawn up at the start are apparently up for negotiation. Good fences make good neighbors, as they say.
Note that I have no experience in such matters, I can only offer a fresh, hopefully clear, perspective. Good luck.