Cool let's add it for flower pots for convenience
Good point, you are right
You are correct. I did not understand your approach at first. I thought you were suggesting every mod adds their own flowerpot item that players need to craft (<plants:flowerpot>, <bop:flowerpot>, etc. each with their own recipes). After reading your approach again what I believe you are suggesting is that mod devs add click functionality to their potables to check if they are being clicked into a vanilla flower pot, and if they are replace the pot with that mod's version of a flower pot which can hold the plant. Then if the player breaks the pot it drops the flower and a vanilla pot (not the modded one). This gives off the appearance to the player that they only ever have to use one flower pot for all modded flowers (assuming every dev did this). While I get this works I feel like this is a lot of work on the mod dev's side for something that seems like it should be simple. Making it a forge hook would make it more widely adopted since supporting is easier. I realize this is probably a lot of work for the forge team to spend their time on but making it a forge hook seems like a much cleaner approach (possibly less mod id's are used and every mod doesn't need to have similar code to make a copy of the flower pot).
I expect 99% of devs that are adding a flower or sapling just want it so players can place it in a flower pot like all vanilla flowers and saplings