I really prefer it this way.
It is not a boolean function, like 'isValid' that would be either valid or not.
This is instead a check function and in theory 1000 things might go wrong.
It is true there is only ONE error code right now, but this can easily change in the future.

Just look at this code snippet:

if (formatCheck(ciP) == true)
  XXX;

What does that mean?
That it HAS checked ciP?
What about the outcome of the check?
No, doesn't make any sense.

It would make sense if the name of the function is changed, for example to formatsOk or formatsSupported.
I prefer to leave it the way it is currently though.