RAH does this sort of thing again (and at about the same time in his career, IIRC) in Friday. The coded signals at the breakfast bar communications screens throughout North America ("you have (n) days to live... ") deliver a consistent-SEEMING message which falls apart when you try to analyze it logically.
I once tackled those messages cryptologically here in AFH, and the only possible "key" I found was the call codes in the messages - the alphabetical sequences in the call codes ("LEV," et cetera) seemed to be references to books of the Bible. If you try to seriously tease out a meaning, you make a logical pratfall (of course, it wouldn't have been the first one I made in this NG :-) ).
Thomas Easton arrived at pretty much the same conclusion about Friday (in his review of the book in _Analog_) as the one reached in the Heinlein Society essay you quoted - that the coded messages are an "in-joke" designed to fool those who think themselves MOST familiar with the RAH canon. The obvious candidates for "fool-ee" would have been Alexei Panshin and H. Bruce Franklin (Venceremos 'Brigade' veteran Franklin looming especially large as a sententious sucker ready for pants-ing with a literary hoax - and in Lazarus Long's description of the "Critics' Lounge" in _TNoTB_, he actually foreshadows such a prank).
David Silver describes what may have been RAH setting Franklin up for hoisting by his own petard in an AFH post:
https://groups.google.com/group/alt.fan.heinlein/browse_frm/month/2010-03?pli=1
"Four years after his hiring at Rutgers, in 1979, Franklin was
commissioned by an editor from the Oxford University Press to write the
first of a projected series on science fiction, the first volume of
which was to be entirely on Heinlein. He contacted the library at UC
Santa Cruz to research the Heinlein papers collection. He had earlier
written Ginny and also asked the archivist to arrange an interview with
Heinlein. Heinlein, convalescing from his cranial by-pass surgery
earlier that year but aware of Franklin's notoriety, after two weeks of
discussion with Ginny and the archivist, agreed to see him and spent a
full day in August with Franklin, the well-known interview when, as
Franklin entered the front door at Bonny Dune, US Navy reserve Lt. Cmdr.
Ginny Heinlein went out the back.
During the interview, Heinlein evidently told Franklin he was in the
process of rewriting _The Number of the Beast_ and agreed to send
Franklin a copy of the final draft to review and include in his book.
Perhaps in exchange Franklin agreed to send Heinlein a copy of
Franklin's final draft to review. Both complied. Franklin wrote his
final chapter to include a review of Number; and Heinlein evidently
communicated his input regarding Franklin's draft for Franklin in his
forward thanks Heinlein for his kindness including correction of some
errors and, even, arguing him into a change of mind in some unidentified
points.
Nevertheless, Franklin's book concludes by consigning, finally, most of
Heinlein's writings including his latest (_The Number of the Beast_) to
what his branch of political thought considers the slag heap of the
failed historical concerns of 20th century America, those of a people,
or culture "undergoing extreme stress and transformations," with what
this critic described as having "no chance for heroism and glory,
because all enemies are imaginary, all goals equally illusory, with the
only combat the battle of the sexes, where the prize is a papier-mache
relationship with a being one creates in one's own mind." _Robert A.
Heinlein: America As Science Fiction_, at 210-11."
The hilarious subtext to that last quote only becomes obvious in retrospect AFTER the Cold War, when Franklin leaps off his ideological high-horse long enough to write America's epitaph intertwined with RAH's - the epitaph itself being informed by Franklin's Marxist outlook. Postmodernism itself is getting ready for another such pratfall.