I guess there's pluses and minuses for either sex both ways, whether bitches are allowed to run in season or not.
For the bitches, I do know for a fact, that there are many who do go through emotional changes while in season. Some become very soft - softer than normal in their work. Some just act like they are out in space somewhere. Some can do a little work and then just lose it. In these cases, most handlers feel like they are just beating their head against a wall to try and work these girlies. So, let's say, BIS are allowed to run at trials and you take your in season bitch who is having major emotional issues to a trial and *expect* her to do well, is this going to go well for you or your dog? Are you really going to pull from a trial or are you going to say to yourself you'll just "go for fun", when we all know when you get there it won't be fun at all for your dog...be honest with yourselves.... In my classes, I say take those 3 weeks off. It's just not worth it to the handler, the dog or their training program.

There are some females who act like nothing has changed in their life - what a relief to have one of those. But, they have been in the minority in my experience.
I also have problems like Lin Battaglia - coyotes. They come looking for a food source (my sheep) and then get doubly interested by bitches in season....great....

(There's things folks who come for lessons just never think about or realize because it's beyond their realm of reality...)
Now, there may be a whole ton of folks like Karissa who own intact males and have (probably) taken the time and found the opportunities to train their boys to do their work and ignore bitches in season. Honestly, I don't know a whole lot of them. I *do* know a whole lot of folks with intact males who use bitches in supposed season as a reason why their dog didn't do well. Oh my gosh, the *anger* at someone who has a suspect female! Sitting on the sidelines hearing this....ugh. If bitches in season would be allowed to run, I think this is going to just get worse....maybe not the anger but the excuse making....double ugh.
A long, long time ago, in the herding world, bitches in season were not allowed to run. Then they decided that should change and they allowed them to all run at the end of the day (no matter the class level). That was a total pain and seemed dumb so they changed it so the bitches in season all ran at the end of their class. Well, that was a pain too, and seemed dumb so now they all just run in order. No matter where the girls run, some males (intact or not) will still quit working to sniff. The scent lasts longer than overnight and certainly just the time of building a course will do *no* good whatsoever to alleviate the issue. (They don't wear panties either, so in herding we won't suffer the "Great Underwear Revolution"!!! hahaha! Thank you for that!! I LOVE it!!!) In herding, at least the dog's instinct will (usually) keep him working - there's no "instinct" really in doing agility so that's not going to help.
Personally I don't feel bitches in season should be allowed to enter because some of their owners don't always make good choices for their emotional girls, none of us want to hear the bitching from some intact male owners and no matter what plans are made to "alleviate the smell" (panties, start line rugs or whatever other pain in the butt hoops you make them jump through), it's still going to be there for dogs who have an amazing sense of smell that we can't even begin to understand.
Guess I'm glad to see/hear that the results are not in favor of this. I don't even have a horse in this race as all my are altered - did the breeding thing, done with it. Nowadays, I want to be able to run my girls any day of the year I want to enter something.

Just my humble opinion as always,
Kyle