Do the Lost Dungeons of Tonisborg Constitute a Megadungeon?

The question is, were megadungeons a feature of D&D during the pre-publication days or shortly thereafter?

Let's review, the information available about the Blackmoor dungeons show a small dungeon. The information available about the Greyhawk dungeons are they too, are a small dungeon, with each level of Gygax's original dungeon limited to a single 8.5 by 11 sheet of paper.

So how about Tonisborg by Greg Svenson? Like the other two dungeons it is a very nice dungeon, larger than the Blackmoor dungeons going by The First Fantasy Campaign information, and smaller than Greyhawk. So it is another small dungeon. The only megadungeon from the early days that I am aware of is from Arduin and if IIRC from a site that is now only partially existent in the Internet Archive, that dungeon had over 100 levels, although the size of each level is a mystery to me. 

So Tonisborg is a great dungeon, but also not a megadungeon.

Some claim that these are megadungeons, but nothing proving that has been published that I am aware of. I have seen nothing on the last, but if it is a megadungeon that would be a surprise. The below is quoted from the first forum of which I have been speaking.

- DA's Castle Blackmoor - published twice (JG and d20 versions)

- EGG's original Castle Greyhawk - mostly unpublished save some extracted pieces

- RJK's Castle El Raja Key - first version mostly-published via ERK Archive and some extracted pieces (S4, S3, WG5, etc.)

- EGG + RJK's expanded Castle Greyhawk - mostly unpublished save some extracted pieces

- PB's Jakhallan Underworld - unpublished but soon to be published by the Tekumel Foundation