`-e READ_ONLY` vs `-e READ_ONLY=true`

[xmontero]

The readme says "Adding -e READ_ONLY will cause the exports file to contain ro instead of rw".

Running this with -e READ_ONLY:

docker run -it --rm --name nfs --privileged -v /tmp:/nfsshare -e SHARED_DIRECTORY=/nfsshare -p 2049:2049 -e READ_ONLY -e SYNC=true itsthenetwork/nfs-server-alpine

it says:

The READ_ONLY environment variable is unset or null, defaulting to 'rw'.
Clients have read/write access.

It says rw when it is supposed to be ro.

Nevertheless with -e READ_ONLY=true like this:

docker run -it --rm --name nfs1 --privileged -v /tmp:/nfsshare -e SHARED_DIRECTORY=/nfsshare -p 2049:2049 -e READ_ONLY=true -e SYNC=true itsthenetwork/nfs-server-alpine

it says:

The READ_ONLY environment variable is set.
Clients will have read-only access.

Should the README be updated? Or am I missing something?