I like it because it does open the door for people who must lower their risk of exposure to possibly show. It’s a great start. 
However, several nits to pick …
According to these rules, “Anyone who exhibits COVID-19 symptoms …”, rather than "Anyone who tests positive for Covid-19 on the day … ". In my county, only 8% of people with covid symptoms sufficient to get the test, actually test positive for covid. Or in other words, 92% of people with covid symptoms, don’t have covid.
Also, people with active sneezy-coughy allergies can’t show. The symptoms are the same as covid-19.
The temp thing is going to be problematic because nature does not make a standard product. Human normal temperature varies and some people are on the high side and could be excluded, even though they are healthy.
Plus, heat, activity, eating and stress can temporarily elevate a person’s temperature, and horse shows tend to be heavy on all (maybe not eating!). Maybe even when entering the front gate. Even a hot or cold beverage can temporarily influence temperature. However, it would be fair enough to put the burden on the people to be tested to make sure they get to the testing without all of those potential variables.
I’ve heard a solution of having people keep a log of their normal temp for two weeks before the first official measurement.
The limitation on entries and on stabling (which also restricts entries) is definitely understandable, but makes it harder for a show to be financially viable.
BUT – What’s good is that we are moving forward here, and that matters. It’s never perfect on the first try. As long as there is continuing learning and progress on these requirements, this is a good start.
>>> What is not mentioned, and what would be the real answer to all of this, is a covid 15-minute test for everyone that comes through the gate. Testing needs to be the solution above all other solutions.