It's because citrus at high concentrations kills earthworms. Citrus in compost in normal quantities relative to other compostables seems to be fine, but you shouldn't be trying to compost a huge pile of just pulp and orange peels in your back yard.

As for why this worked here, I'm sure there are a whole lot of things that aren't earthworms living in a formerly rainforested spot in Costa Rica which can break that stuff down over 15 years.

But there is a lot of growth. Which makes me wonder why people say to not compost citrus peels.

That was my reaction too! I read the headline and immediately thought "oh god they killed it didn't they". I was shocked to find out it was a resounding success, at least in comparison to the alternative of doing nothing.

It's probably got something to do with local soil ecology or rainfall amounts, so there may still be some merit to not composting your orange peels, but this definitely makes me want to learn more about why this guidance is so heavily repeated.

A juice company-sponsored scientific article finds that juice company waste is good for the environment?

How could this be?

Historically, peer review has not been enough to weed out positive publication bias and outright fraud even when there was no profit motive. With a United Fruit Company/Dole-tier juice company breathing down your neck? Science... finds a way.

Rodents. Most people don't compost properly - they leave out the cover material on the sides and top, and still believe the myth that compost needs to be turned.

The fruit smell attracts rodents. Enough cover material keeps the smell in and the edibles inaccessible. Then you can compost most of the foodstuffs you're normally told not to (fruit, animal products, dairy, etc.). Oil is still a no-no, as I recall.

There's a photo of the sign near the end of the article. It's not yellow but it has yellow writing.

I guess it depends on the dog, chihuahua or Jack Russell, not so much. But a Doberman, or boxer sized weasel would be frightening.

I might be misunderstanding what you're saying, but don't we already do this?