It really depends on how you set it up. If you prefer, you can choose to split non-sensitive environment variables and sensitive secrets into different projects - and use them for different purposes / in different ways.
It very much sounds like security is an after thought.
Seems cool if you need to sync env vars, but you should probably just be using battle tested etcd+confd or console+console template.
This product seems to be based on some incredibly misguided principles (from a security perspective). I don’t think a technology like this has any place in a modern enterprise.
Part of the whole point of using a secret manager is to avoid storing them in environment variables.
That coupled with the lack of an API and the use of MongoDB are just too many red flags for me to ignore.