Explicit Prohibition on Nested Tables?

A comment just came up on the Framemaker 13 prerelease forum to the effect of "DITA allows nested tables so Framemaker should too".
I don't think that assertion is correct.
DITA uses the OASIS CALS Exchange model, which explicitly disallows the full-CALS <entrytbl> element.
That seems like a pretty clear indication that table nesting is not intended.
However, I couldn't find anything in either the CALS interchange specification or in the 1.2 spec that 100% says "tables cannot nest".
The problem is that the grammars cannot themselves disallow nested tables because <entry> allows block elements that then allow tables (e.g., <p>).
I'm wondering if the language reference for <table> or <entry> should have an explicit "tables may not nest" statement or if the rule should be something like "DITA does not intend tables to be nested. Processors MAY support nested tables. Processing interchange is not guaranteed for documents that include nested tables."?
Cheers, Eliot ————— Eliot Kimber, Owner Contrext, LLC http://contrext.com