Par in DG is clearly not as useful as BG par primarily since their 2-putt integer mnemonic works but is off by a half-stroke for DG. Allowing half-stroke pars like 2.5 and 3.5 would be more useful, but traditionalists would reject them as not golf-like, a case of decadisophobia (fear of decimal numbers) although handicaps use decimals.
An error is any reason you don't earn the expected (birdie) score whether it was weak execution, mental or physical throwing mistake, a bad break or a penalty. The focus is on what score the player would be expected to throw based on the challenges present on the hole.
That's how many competitive players think. They figure out what's the score they could consistently make on a hole with good throws to determine their personal perfect round on that course. Competitive players don't really dwell on par on new holes other than as a rough clue that it might be tougher than a typical par 3. A score of par or higher on a hole occurs when you didn't get your expected score goal. How you end up with a par or higher score doesn't need a label other than for stats.
As a designer, it would be easier to design holes based on best expected score for a skill level (then add one for par) than try to figure out the scoring spread to come up with a par value that matches the current definition.
For those who wonder how CK can come up with this stuff, remember that the pre-definition idea of "Par = Reach+2" is ossified into his brain. That's the starting point and ending point for all his thinking on par.
There is no 2-putt mnemonic in disc golf. There has not been one since at least 1997 when the definition was first published and did not include the words "putt", "plus", or "add". Only those stuck in the "Reach+2" ancient past think there is a 2-putt mnemonic.
Chuck thinks par in DG is not useful because Reach+2 is not useful. If we look at actual scores and pars set according to the definition, not only is DG par as useful as BG par, it is virtually identical. Take any BG scoring distribution, use the DG definition of par, and you will get the same par as BG uses.
(Except for the one or two fake par 5s in golf which everyone knows don't really reflect par but are set to generate fake scoring excitement.)
This may be evidence that there is a "final two throws" in DG. If so, that last throw to Reach is a layup, already accounted for as one of the final two. So par is the expected score in both sports, not the expected score in one sport and a bad score in another sport.
I'd argue DG par is MORE useful because we cannot know as much about expected score by merely looking at distance like BG can.
There are no half-putts, nor are there any half-scores. It is impossible to expect a score other than an integer because no one can get a score other than an integer.
You would not be able to find any evidence of one-half fewer putts in DG by looking at scoring distributions. The general shape of the skewed hump distribution is the same no matter how many putts are expected. BG or DG. Each distribution is a result of a series of throws/strokes which have an increasing probability of completing the hole. For the same average scores, you would not be able to sort a bunch of scoring distributions into DG or BG piles.
(Except our island holes would stick out like a sore thumb.)
In the past, and still in Chuck's mind, players thought they needed a birdie to keep up because way back in ye olden days "Reach plus 2" was the way par was set. While it is true that a score of Reach+2 would involve an error and would cause players to fall back, the actual definition of par does not allow for one error per hole.
Now that more events are actually setting par according to the definition, you hear more and more that "par on this hole is good"; and that's for the elite players on video who are better than experts. Players these days recognize when a score of par will let them keep up with the field. There is more commentary along the lines of "a hole that hasn't given up any birdies is not the hole to take risks trying to get ahead of the field".
As for designing holes, nothing changes except you skip the step of: "(then add one for par)".
I generally agree with the paragraph starting with "An error is any reason you don't earn the expected ..." except for your Kevin Nealon's Mr. Subliminal attempt to slip "(birdie)" in there. Also, we need something shorter and less circular than that paragraph if we are to fit it in the definition.