At the very least, it looks like the manufacturer didn't have the time (or at least the desire) to develop a PCB specifically for the device.
On the other hand, sometimes even large companies do the same. About 30 years ago, I remember, we got new laboratory equipment for several tens of thousands of dollars, which had a regular color TV instead of a screen. A real TV, right in its original case, just like the ones you buy in the store.
That's practical, you can watch news and then keep on working.
Chinese clone.
So?
Lot of people like to hack/flash their devices to better suite them for their purposes. This build makes it very convenient.
So if price or size is not a factor, I don't see anything wrong.
But the choice to deliver a device with development board planted to it gives me some doubts about the state of development .
Years ago my late company built thousands of solar charge controllers. I still have one. They used pulse with modulation to control the current, A UNO is many time larger than the boards we built and will require a separate power source where ours were powered only by the solar panel. So, no, you have an amateur built device that probably never worked.
I used to have to cobble together bits of kit for use in professional contexts.
Given that no off the shelf product was available, it was as professional as it got.
Frankly, as long as it got someone out of a pickle, no-one questioned it.
Some of it was good enough for a manufacturer to put into production.
It wasn't an Arduino but a Crouzet mini PLC.
Hundreds of them went into service.
Someone made some money, not me.
Well, in Brazil you cannot consider something "professional" if it was developed by someone who is not formally qualified to do so. That being said, if the UNO (clone or not) was on the product by design of an EE and got the necessary certifications, it would be considered professional.
I might add, many professionals use development boards before moving onto a more finished product.
On balance, you might not use a development board in a finished product.
It rather depends on the circumstances.
A consumer washing machine with an Arduino board in it might raise some eyebrows, but an Atmel processor on a "professional" PCB would not.
If you build it in, you have to take care that the tube is at 20kV, the metal frame inside may be at 230VAC and it has pretty strong magnetic fields.
Outsourcing seems like a smart idea.
Also, in our lab, we had stuff with built in TV tubes. Once they break, there is no replacement for that very specific size and form factor
Low volume early production…
or very small market oooortunity.
Get the units into the field aftter testing quickly.to prove the idea and principles.
Is the soldering and assembly is of good quality ?, does the unit do what says on the box ?
Same chip and software is being used.
Does it live outside? If yes then an automotive variant of the processor should have been used.
I vaguely recall stories, here in this forum, of the non-automotive processor behaving erratically when the high temperature limit was exceeded.
Well that's what I'm from meaning too, why would it be worse than with another professional board? When it does what it has to do and can work safe? I don’t see a problem in it then. I used an old K8000 microprocessor in my greenhouse to control the climate. Was this professional? I don’t think either but he worked for almost 25 years in very hard conditions like relative humidity above 70%.
While it could work perfectly and do not violate any specs, I would feel uncomfortable to use defibrillator if I knew there's Uno clone inside. 
I'll wager you would feel even more uncomfortable if you didn't use it.
until you saw the source code and recognized it from a forum discussion ....
..where I personally offered dirty quick hack solution thinking it was mosquito racket...
My oldest Arduino Uno R3 clone will reach 100,000 hours of operation this October — so nobody has to do the math: that's about 11.4 years running 24/7 — without a single failure.
So there's nothing wrong with that!
What kind of program? just interested.
(no power interrupt either?)
It controls the circulation pump of a solar thermal system. It has no on/off switch and normally runs 24/7. Power outages do interrupt it, of course, so the 100,000 hours are accumulated operating hours, not one uninterrupted 100,000-hour run.