In article . com,
wrote:

The best AIM reference I can get you is in 4-3-21: "If pilots wish to
proceed in accordance with instrument flight rules, they must
specifically request and obtain, an IFR clearance." So you would have
to say something like "Request an IFR clearance to Podunk airport via
the ILS runway 26."

Just requesting the ILS is ambiguous at best.

In this case there was no ambiguity, at least not on my end. I
specifically requested a practice approach in VFR conditions (I used
both phrases). I got back something that sounded like it might have
been an IFR clearance ("Cleared for the approach", but not "Cleared TO
anywhere", but also (notably) not "practice approach approved" and not
"maintain VFR.")

Then I specifically replied that I didn't want a real approach, I wanted
a practice approach, and ATC responded that I "had to be in the system"
(whatever that means). Notably they did NOT say anything along the
lines of "Acknowledged, maintain VFR at all times."

It was a very strange situation, hence my question.