TOPIC: What is a True Grind?

Hello, I'm new to True Dungeon as of GenCon this year and I'm excited to do more. I see that there's an event categorized as a "True Grind" coming up at Gamehole Con. I've seen a few passing mentions of what a True Grind is, but nothing definitive. I've checked the PHB, the resources page, the first few pages of the forums, and the FAQ to no avail. It looks like the event listing is only for one hour, so is this a shorter-style event?

Would some kind soul be able to explain the difference between something like a regular convention adventure or a VTD and a True Grind?

Convention adventure: Organized, gentle, methodical
VTD: Same as above but virtual

True Grind: in-person onslaught of enemies. Tight deadlines with completion, massive amounts of damage. Typically bought and ran by experienced players with tokens to cover the "oddities" that could occur (weapons overheating so you can't use them, players turn on the party, etc.)

Would recommend trying it once if you can snag a ticket, but getting a ticket can be even more painful than a True Grind run.