Vouchercloud spokesman Chris Johnson said: "Taking a break once in a while is by all means OK - in fact, many high profile business leaders recommend taking regular breaks in order to make you more productive. But, taking calls from your friend or partner and checking social media might be pushing your luck."
The results come as the push to hit the brakes on out-of-control workloads gains steam globally, with a number of countries experimenting with, and reaping productivity benefits from, reducing hours.
According to the UK-based New Economics Foundation, a "normal" working week of 21 hours could help address a "range of urgent, interlinked problems", including "overwork, unemployment, over-consumption, high carbon emissions, low wellbeing, entrenched inequalities, and the lack of time to live sustainably, to care for each other, and simply to enjoy life".
In 2014, the Swedish city of Gothenburg began trialling a six-hour work day for government employees, with some private businesses joining suit.
"Our employees produce more than similar companies do," Maria Brath, chief executive of tech firm Brath, wrote on the company's blog. "We obviously measure this. It hasn't happened by itself, we've been working on this from the start. Today we get more done in six hours than comparable companies do in eight."
And according to CNN, a number of forward-thinking companies in the US have implemented four-day work weeks, noting an improvement in staff morale, retention and quality of output.
One former World Bank policy expert told CNN two theories were key to his 20-hour work week: "Parkinson's law", that work expands to fill the time available, and the "80/20 Principle", that says 80 per cent of productivity is achieved in 20 per cent of our time.
"The thing that got me the most was if you look at the time you're actually at your desk, how much is actually working, compared with looking at Facebook or getting a cup of tea," Ms Smith said.
Michael Henderson, a "corporate anthropologist" who runs New Zealand-based advisory firm Cultures at Work, agreed that the 20-hour week could be beneficial, but only for certain personalities.
"Some cope well with it, and others not so much," he told news.com.au earlier this year.
"My sense is that some individuals almost need the discipline of being in a certain place at a certain time for a certain number of hours to deal with the workload. Others are far more self-regulating and disciplined."
He added that the other big caveat was the customer or client.
"It's all very well from an organisational point of view - we can be more productive, pay people less to do less but achieve more - as long as you don't take your eye off the ball of the customer," he said.
But the New Economics Foundation's solution to the lower earnings as a result of a much shorter working week would require a considerable societal changes.
They include an increased minimum wage, a "radical restructuring" of government benefits, "more and better" public services, and "encouraging more uncommodified activity and consumption".
