Supporters and Using "On Top Of"

In 8.13 of Writing with Inform, two specific wordings are given:

if the genie’s lamp is on the table …
if the genie’s lamp is on top of the table …

However, one of my students sent me this code:

[code]The Learning Lab is a room.
A supporter called the grill is in the Learning Lab.
A steak is on the grill.

Before waiting in the Learning Lab (this is the objects supporting objects test rule):
if the steak is on the grill, say “Steak confirmed as on the grill.”;
if the steak is on top of the grill, say “Steak confirmed as on top of the grill.”[/code]
This results in a error:

Problem. In the sentence ‘if the steak is on top of the grill, say “Steak confirmed as on top of the grill.”’ , I was expecting to read a condition, but instead found some text that I couldn’t understand - ‘steak is on top of the grill’.

I’m not sure why this error is coming up in this context since 6.11 in the manual says “the relationship here is one called support (being on top of, in effect).” So it seems like the grill (which is a supporter) is the right kind for this check. What am I missing?

Looks like a straight-up bug. The standard rules declare “The verb to be on top of means the reversed support relation,” but this doesn’t wind up getting parsed.

Okay, good to know. And actually I’m happy about this! Not so much that Inform has a bug, per se, but the context is that I’m having my students write up a series of very focused tests that prove out behavior. For example:

Before waiting in the Learning Lab (this is the objects supporting objects test rule): if the grill supports the steak, say "Grill confirmed as supporting the steak."; if the grill is supporting the steak, say "Grill confirmed as supporting the steak."; if the steak is supported by the grill, say "Steak confirmed as supported by the grill."; if the steak is on the grill, say "Steak confirmed as on the grill."; [BUG! if the steak is on top of the grill, say "Steak confirmed as on top of the grill."]
So the part I’m happy about is that this approach is showing them how to break down a system and test it with the simplest possible tests that also demonstrate and document behavior.

I threw in a bug report: inform7.com/mantis/view.php?id=1361