Yes, there is that too. Some elders do things just because it was how they were taught and there is no better way for them. I agree, it is a hit and miss when following their advice. The only real test is whether it provides results for you. I did some looking and from what I found on crop perspective was:
Leafy vegetables and flowers that produce yield above ground and don't rely on extensive root development do fine when planted during the waxing moon.
Crops that produce their yield below ground, root vegetables such as beets, carrots, parsnips, potatoes, onions and turnips do better planted during the waning moon. This position of the moon encourages development of root growth and tree bark instead of forcing the plant to proliferate above ground before it has a strong grounding. Saplings with firmly established roots are less in danger of damage and deterioration due to loss of branches or top growth during the winter.
Full moon planting creates more moisture in the soil so in droughts it advises to plant closer to this time. The waxing moon is the time to encourage rapid new growth. If you want to retard or control growth, or encourage hardy rooting, perform the necessary activities during the waning moon.
Whether that gives more crop or not and does better I have no idea but it seems to be a strong conclusion by many supposed research. I don't have an area to garden at the moment but I will try it in the future to see the results now that I am curious. lol
For bow making, some natives cut the wood during the new moon on a high hill. The way the water drains makes the grains in the wood tighter, which in turn makes casting time faster for shooting.