[Fuck For Fun]

You need use forward:

client_infochanged

test:

public fw_SetClientKeyValue( id, const infobuffer[], const key[] )
{
    // Block CS model changes
    if ( g_has_custom_model[id] && equal( key, "model" ) )
        return FMRES_SUPERCEDE;
   
    return FMRES_IGNORED;
}