Rocket League’s Terms of Use (Section 3.2) explicitly forbid "any code or software not expressly authorized by Psyonix that interacts with the game." Unlike BakkesMod (which is tolerated because it does not give competitive advantages or unlock paid cosmetics), Miku Client is known to trigger EAC (Easy Anti-Cheat). The "fixed" version may claim to bypass EAC, but anti-cheat updates weekly. A single detection leads to a permanent ban, losing your entire inventory (worth potentially hundreds of dollars).
: In the context of modding, "fixed" usually refers to an update released by the client developers to bypass recent Rocket League security patches or anti-cheat updates. Anti-Cheat Impact miku client rocket league unlock all title fixed
If you still want to test the "fixed" unlock all title feature, here is the current method as per community guides: Rocket League’s Terms of Use (Section 3