Yes, I researched "Harvesting", which I don't recall seeing in previous betas, and it supposedly unlocked gardens, but gardens were already available to be built.

Actually I think the R&D for gardens improves the food output of the gardens.

As for the old techs remaining perhaps they will add more buildings in their place. Because now that they limited most buildings to 1 copy it would be cool to see more buildings. Before there was no need as specializing a city simply meant you build a ton of one type of building their. Now that most buildings are limited to 1 cities tend to look alike since you have more space then you can fill.