I have owned both the Suunto Core (in various models) and the Casio ABC watch (PRG270) and used them in hiking and up on mountains. I mentioned my experiences taking the Casio with me here
https://www.watchuseek.com/f296/three-months-travelling-protrek-prg270-pic-heavy-1308290.html instead of the Suunto. I posted the reasons for my choice there, and they are very similar to the reasons mentioned in the article from your link.
I quite like the thermometer on my PRG270, and have calibrated it with a more accurate probe sensor thermometer, and it is still very closely synced to it. I calibrated it to the Suunto I have as well, and both seem to be reporting the correct temperature - the Casio shows temps to one decimal place, the Suunto rounds to nearest degree. I haven't calibrated it since, (almost 10 months ago) and it still corresponds with the probe sensor. But you need it to be off wrist for accurate temperature. I usually wear it on my backpack sternum strap when hiking, but if it is raining I have worn it on the outside of my rain jacket, and have found that in cooler climates my body heat doesn't transmit out through my midlayer and rain jacket to affect the temperature reading greatly. Also direct sunlight tends to increase the temperature reading significantly - like leaving the Casio on a window sill to charge up, it will report a higher than actual temperature.
For me the A (altimeter) functions work well if it is calibrated accordingly, and you understand that it is affected by weather and temperature changes. If it is a calm day the lower pressure while ascending on a hike registers as an accurate increase in elevation on the watch. I've set my GPS to record barometer chart as well as the GPS elevation (with barometric altimeter turned off), and have compared that with manual records of the barometer readings reported by the Suunto Core, and both were close. I haven't done the same with my Casio as yet, but should do that on my next hike if I remember.
The B (Barometer) function again works well, when you recognize that the Altimeter reported from the above is derived from the barometer through a mathematical relationship. I tend to use the B function more when walking that the A function as a guide to the weather. Of course if on mountains, you need to be aware of the corresponding normal barometric pressure for the elevation you are at for you to understand what is happening with the weather. So as an example, if I am at 8000' (2438m) elevation the absolute atmospheric pressure should be around 753hPa (22.2inHg / 564mmHg). Then while I am this altitude, and the watch says 750hPa, it is not because the weather is turning, but because I am at this altitude. But if the watch shows <700hPa while I am at this altitude, it could be a sign that the weather is turning. You also have to be aware of pressure changes caused by windy conditions and your physical location when taking the readings. I made a small excel chart of air pressure/elevation based on the mathematical formula. A similar chart is shown here
Air Pressure and Altitude above Sea Level
For the C (compass) function, I've found it to be mostly accurate. I haven't used it for navigation while hiking (I use my real compass and GPS for that) but have found it handy traveling in new cities when I have a tourist map and I need to quickly see which direction I'm facing. There have been some glitches on my PRG270 compass though. I noticed it was pointing in the incorrect direction while I was traveling and had to try re calibrate it. I can't reproduce the error, and it has seemed to be functioning correctly since.
