We try not to make assumptions, whenever possible. There are probably several thousand cases where two separate filmographies in the database belong to the same person. But there are probably as many cases where the opposite is true. You'd be surprised at how many different people working in the film industry have similar or identical names (no matter how uncommon).
A small spelling variation or a different middle initial may be a typo, or may be evidence of a deliberate attempt to differentiate two separate careers: even identical names belonging to people with similar careers may not constitute proof that two people are the same (there are several cases of sons with the same first name as their father following in their parent's footsteps and dropping the "junior" from their name: a well-known example is Jason Robards).
We try to err on the side of caution and unless we're reasonably sure that two identical or similar names belong to the same person, we prefer to leave filmographies separate until we have more info or proof.
If you are positive that two names belong to the same person, you are welcome to submit a correction (click on the "update" button found at the bottom of the person's filmography and choose the name correction option, or supply an explanatory comment, and our editors will take care of it).