This is the folder structure of Evo in the steam install.

Look familiar? It should. This is what you would get if you grabbed the weblobby archive from ikinz' google drive or from the evo download page (goes tot he same place).
Hmm I notice that evo_data folder... what's in there?

To explain... Weblobby takes a param that makes "evo_data" it's spring datadir. It still reads from the common folders, which is why if you're an existing springer and you grab evo via steam, weblobby will still show all the shit you have from your spring common folders. Evo keeps itself clean and tidy this way, ensuring that when a user deletes evo from steam, it doesn't leave a bunch of crap behind. Moreover, it makes it more compatible with people who want to play other games like ba or s44.
In this way, it can have it's own stuff, but not conflict in any way.
"evo_data" is pretty much exactly like:
my docs / my games / spring
in a different location, but weblobby still reads both locations. It's really quite simple. If you are one of the people who has been confused about this, please stop spreading bullshit. It's very irritating.