I agree that the safest and probably most optimal start is the three earths and wait to see if they go in for early aggression for the optional CA. In fact, its a pretty risky play to do the tree start against an order player because, as you said, they can mass swords, which will force you to mass earths and you'd need to constantly be harassing their eco to counteract yours (which is likely 1 miner 1 praying for death blossom or 2 miners at most).
The problem with them splitting their army to attack your eco is that they leave their own exposed. And you can simply garrison your own eco while picking away at theirs. Or, if they decide to hide their own eco, you're at a stalemate in terms of no gold production. The thing is, a tree at their gates is more threatening than 2 swords or 3 cats at yours.
What I like about this strategy is that the average order player isn't expecting early aggression in the form of a treature and will prioritize their attack on the tree which tanks their swords, while the scorps can pick off miners. Additionally, because of the earth's 4 second creation rate, you can get the center early, and, assuming you held it, can collect a good sum of gold while harassing your opponent to somewhat make up for your lack of miners. This strategy usually leads to a quick and decisive victory or defeat against an order. If you can freeze their archer and get 2-3 punches with your earth right after you capture the center, you can guarantee a kill on that archer with combining then blossoming.
As for EvC, I find that even if they mass cats, they won't do enough damage to take out your tree. Death blossom (I think) 1 shots cats, if not nearly kills them, so they won't be able to build mass fast enough to be a threat. Additionally, because you send your first 1-2 earths to support your forward tree, it shouldn't fall even if you lose all 3 of your scorps at the same time; further, a lot of chaos players default to throwing in a few bombers which pretty much do nothing to trees. I'd say this strategy is better EvC than EvO because mid-late game EvC is nearly impossible to win against a chaos that masses eclipes whereas with EvO you have more options. So therefore, because this is an early-game attempt to finish the match quickly, it is my most preferred method against chaos players; even moreso than air/fire or 3 earth starts just due to the tankiness of trees and 3 unmicroable attacking scorps.
One last point I'd like to make is that the 3 earth start can be combined with this strategy if done fast enough, but it lacks the same shock and awe and by then, they will have enough eco to quickly purchase a CA of their own, which will force you to either pull back your tree out of range of using DB on their miners, or force you to commit to the attack hoping they don't just pull their miners into the base.
