Joseph: Somewhere on “social media”. It was reported in the CR but was deleted by a moderator.
While I will not comment on whether this “siyum” was lavish or not, one can hold “siyum” during the nine days. The Ramah states it in 551:10 and the Mishna Berurah elaborates in SK 73, 75-78.
I also question why someone has to make it on Rosh Chodesh when (by the Ashkenazim) the nine days just started. I wonder why he couldn’t make the siyum on Sunday……probably because his chevra were in the Catskills.