Here is a strange promotion for tourists to visit Yorkshire show caves, from the pages of Yours magazine, 16-29 July 2019. If the words encircled are too small for you to read, it says:

"CAN'T GET ENOUGH OF CAVES?
Just a 20-minute walk away, Ingleborough Cave is reached by a lovely 1.3-mile ramble along a nature trail, starting in the quaint village of Clapham. Follow in the footsteps of the early Victorian explorers as you journey through 450 million years of geology along awe-inspiring passages that are brought to life by stalagmites, flowstones, scallops, fossils and much more. Its large passages and absence of steps make it accessible for all - a great option if you're visiting with the family!"

Now although it doesn't explicitly say that the picture is of Ingleborough Cave, the fact that there's an arrow connecting the text with the photo surely suggests that that's what it is.

So when the punters who've read this stuff visit Ingleborough Cave, they're going to be very disappointed not to see this huge chamber.

I've heard of a few people turning up at Ingleborough Cave expecting to walk through to GG, so there must be some misinformation floating out there somewhere, although I've never actually seen it before.

The connection between Ingleborough Cave and GG was well publicised when it was first made - and I expect that was what "sunk in" rather than the detail of just how the two were joined. So I think it fits into the "popular myth" category rather than being due to any blatant misinformation, though this particular newspaper bit won't help!