I have followed up on this problem and have been told by Amazon support they understand the problem and are working on a solution. For those that do not understand the issue, its not a smartthings, its a fundamental problem with smartdevices and echo not prioritising the group/group names defined by users over internal searches/services. The voice recognition works and identifies a group/group name but does not activate the group/group name command because it has some internal override for a service.
e.g. to replicate, in alexa app, go to smarthome, define a group called 'comedy', try the phrase 'turn on comedy' and you will get back
'sorry, I'm not sure which app or game to open' or at least I do
this could be a problem for any smart devices, obviously Harmony skill will also be on the horizon, but I still think that the echo is not functioning in the correct way and hopefully support agree and will provide a solution as they have mentioned
There is an odd workaround, add 'lights' to the end of your command, this identifies it as a smart device and runs the group/group name correctly.