Yeah, I think there's a lot of jealousy there from the traditionalists, and the dis-information and wives tales abound. A bit of tall poppy syndrome methinks.
I have worked for several beekeepers extracting honey. Bloody hot, hard work.!!
My hat goes off to the lateral and simplistic thinking of the inventor.
Several of my mates down here have bees, but they all knock the flow-hive. Hive beetle and European foul brood have been around for a fair while, and now there is a more disastrous American foul brood. Some have lost all their bees, their whole income, through disease and quarantine, all because of a few unscrupulous or lazy operators.
The most plausible criticism I have heard is thick honey not flowing, but extracting seems to be done at the end of spring/start of summer, so this should be a non-issue.
I would urge anyone "going with the flow" to join an apiary club, know their diseases and do regular inspections, or the traditionalists might end up as savage as their bees.
That said, the costs and labour involved in traditional extraction are the biggest deterrents.