Thanks Sue Ellen,
You're right, re reading their blurb- "The concept here is that your gas and electricity switches to a new supplier when a better deal pops up - without you doing anything." They refer to "a better deal" rather than the best deal, which would give them wiggle room to move you to a provider that rewards them with more commission as opposed to the maximum savings to the customer.
I just read that article you linked, the Irish company do commit to switching to the best option! I'll check it out.