I don't fully agree either, but some of them make sense. But, some of them do make enough sense for some kind of critical applications, that it is worth to consider the alternatives (although power usage should also be considered).

As items (iii) (although it incorrectly says "(ii)") and (iv) of the caption of figure 1, are reasonable considerations.

There is also the consideration of faulty displays, in case a segment stops working (although you can mitigate this problem somewhat, by adding a test switch to light up all of the segments).

About decimals, one possibility (depending on the application) is to require a fixed position for the decimal point and add a wider gap between the digits at that position, which improves the clarity.

They also mention, "the user cannot see the difference between entering zero, or entering zero then decimal point". This is a problem on many hand-held calculators but it is easy to avoid, by not displaying the decimal point unless it has been entered explicitly (or if the result is being displayed).

Upsidedown (also mentioned in the article) is also a reasonable consideration, although there are ways to mitigate that too.