Welcome to the wonderful world of ad-hoc definitions made at a time before anyone really understood what the internet was, or indeed was going to be all about.
While there's no official definition of the usage of "profile" as meaning a restricted subset of another standard, over the years it has become common use to body's like the ietf to mean just that.
The problem you have here is not so much one of standards, but one of government and academia based red-tape from an age gone by, where groups like the ietf are still run by the old guard who still insist on using the original terminology used back at the beginning.
I don't claim to be an expert in how any of these groups think, but I've been working in I.T long enough to have seen a fair few of these RFC's when they where brand new and first released, and a lot of the terminology exists for no other reason than "Beacuse they can"
Back then when much of this "Internet stuff" was still quite new, and large chunks of it where run by various university and government bodies, many of the departments that started the projects off, had to have ways of making themselves stand out from each other.
Understand that this was all in the days before any of the glitzy marketing and SEO practices we have today, and one way of making your department stand out was to get folks using a common terminology which inherently linked back to your vocabulary, and as a result your projects, ultimately putting you at the front of what that group was trying to achieve.
As time marched on, much of this terminology became set in stone within the various organisations, to the point where there are even standards for how the standards body's are allowed to describe standards to those who use them.
These days, were left with quite a surplus of definitions that don't make a lot of sense to a newer generation, and which in some places could actually be deemed as harmful and confusing.
Think for a moment how much the HTML4 spec was tidied up to accommodate HTML5. A lot of the work involved here was nothing to do with what should or should not make it into the specification, a vast amount of it was simply due to the mammoth task surrounding the existing specifications and re-wording things so that some kind of sense could be made of them.
Your guess as to the intended definition is probably as close as your going to get, and from what I can remember it's certainly accurate, I wouldn't however be surprised if there where definitions that did in fact actually conflict with that.
To be perfectly honest, I wouldn't be at all surprised if there was an RFC available somewhere that actually defined what the various definitions should be defined as in definition documents :-)
Unfortunately my days of remembering what each number on each RFC is/was and what it referred to are long behind me, I just use the various search tools on "rfc-editor.org" these days.