Whoops -- looks like I confused #9 and #19 when checking your list of additions. My apologies for the confusion!
The article in #9 I managed to find, but it was issue #19 where I drew a blank. The only mention of Greyhawk in that issue seems to be a reference to the number of spells per level in the original Greyhawk supplement on page 24. (But no actual Greyhawk lore.)
For #212, there is a mention of WG7: Castle Greyhawk on page p24, but that appears to be a story of one group's experience with the module, and also no new Greyhawk lore.
Might those two references be what you had in mind?