A heads up about Engine Quest heads

so why doesn't a known company like Edelbrock or EQ make sure their heads are a true bolt-on OOTB??? Don't make sense to me, if a common machine shop can go over a head and correct the flaws, why not the manufacture????? That way the "fully assembled heads" are true bolt on.
According to every company that does fully assembled heads, there good to go right OOTB.