Correct. This has undergone some changes recently and will become available with snapd 2.28. Here is the forum topic where this issue was discussed: How to "snap get" root document
You will be able to discover config options easily (in a list format by default if running in a terminal), e.g.
$ snap get core
Key Value
bar {...}
foo 1
refresh {...}
$ snap get core baz
Key Value
bar.baz 2
And snap get <snapname> -d will yield json output with complete configuration of given snap.