The list on the CHIRP homepage is (apparently) generated automatically from the daily CHIRP build, so if the radio is not here, then the CHIRP code does not know about it. Within the CHIRP code, there is (supposed of be) an "alias" defined for any radio that has the IDENTICAL programming interface with another radio. "identical" means completely indistinguishable, including any internal version or ID string.
If a radio is "almost" identical, then the CHIRP code needs to be updated so it knows the differences. If the radio is truly identical, then you can program it using the original name or any of the aliases. If you think you radio might be identical and you are very brave, you can try it: please report the result here. If you think it may be a variant, please consider learning how to "sniff" the protocol, and report the result here. Please do not try any of this unless you are willing to risk temporary or permanent problems with your radio up to and including totally bricking it. (very unlikely but you must take assume the responsibility for this.)