Does the revision media-type parameter in the accept header of the Reactor API work as intended?

I’ve been trying out the Adobe Reactor API and was wondering if others have had the same experience with the revision media-type parameter in the accept header. It might be me, just misunderstand its functionality. The documentation states: 

• All GET requests to the Reactor API require an Accept header to determine what data is returned by the system. In most cases, this value will be application/vnd.api+json;revision=# (where # is the revision number of the resource you want to retrieve, e.g. 1).

However, when I make a request for a single rule (https://reactor.adobe.io/rules/{RULE_ID}) that have multiple revisions, and I use the header Accept: application/vnd.api+json;revision=6. I get a 406 not acceptable.
The only value that seems to work is revision=1.  So my question is: is the revision parameter actually functional, or am I misunderstanding something?

Another question I have, is about the format of the Accept header. It seems standard to allow optional whitespace between the media type and its parameters, e.g.: Accept: application/vnd.api+json; revision= 1. However, if I do that, it also results in a 406 not acceptable.
Do others have the same experience?