Its not about gain, you dont gain more crops per se. Its about harvesting at the best time for best quality. Or harvesting roots for storage when moisture content it low so they store for longer. Thats about it as far as harvesting goes. Planting at the right time shortens the growing season for that plant by a couple of weeks, it gives it a better start. Nothing more to it than that really.
It's ALL about yield gain.
If a farmer can rotate crops faster then trust me, they would ALL be doing it.
Likewise if a farmer could produce healthier and better tasting crops then they would also ALL be doing it.
Supermarkets make up around 80% of the fruit and veg bought from UK farmers, these supermarket buyers are notoriously picky.
You can have you produce picked and packaged ready to go and the supermarket refuse them if they don't look right.
Add to that the fact that farmers are usually forced to sell at very little profit, and you can see that if there was any possible gain, from taste, to storage, from yield to colour they would jump on it with everything they've got.
As i say if there was any evidence that lunar gardening/farming worked even 0.5% of the time then trust me everyone in the world would be doing it.
Imagine Ireland in the 17th century over 1 million people died from starvation.
If lunar farming offered a 0.5% gain in yield then that would have saved 5000 lives.
As i say, if your curious then your hurting no one by giving it a go.
Personally i think it's BS though and yet another superstition.