Yours fits because you are using an 18x10 with a tire that could fit on an 18x8.5. The tire is probably stretched which lowers the profile even more and takes the corner off the tire giving even more room for movement.
Really no sense in buying a rim that wide to use a tire that narrow, unless of course that's the only width available.
Ricgt, wheel fitment is about more than rim size.
The tire you run, the offset, how low the car is are all variables that affect fitment.
is this the same car that lost a wheel on the freeway??? bringing back some memories.