Tunnels

I have known Minecraft for a while now. I know how the game works (mostly), I watch how people play it. But I have never seen something like this.
SInce I'm a connoisseur I decided to look at the Minecraft forums, mainly the first pages. I pretty much found nothing out of the peculiar but I found something that wasn't documented at all.
Here's the post in whole:
"minecraft secret?
pretty sure nobody knows about this but i discovered a new secret.
AFAIK: this only works on alpha 1.0.14 and alpha 1.0.15
step 1: go 20-70 blocks south of where you are
step 2: find a flat position (its rare for it to appear in mountains)
step 3: find 4 holes leading to randomly generated signs at the bottom (can generate from one word up to a full sentence)"
The comments weren't kind of surprised. They mostly believed that it was all just a bunch of hoaxes.
I decided to test it out, some didn't work out, some did. Here is one I managed to capture.
(They weren't covered in wood and cobblestone, after I fell I decided to get some resources to build myself up)
I first booted up Betacraft and chose the Alpha 1.0.15 version, then went somewhere between 60-65 blocks south and I managed to find them. How? I don't know. Procedural generation, perhaps.
My probable guess is that Notch (or others at the time) has secretly implemented this as a thing people should've have never find. But somehow some people managed to find it, revealing Notch's secrets.
Who knows what actually happened?
The first hole contained a sign that just said "collect". Tried collecting some stuff and the sign changed to "forget", Don't have the screenshot though, it somehow didn't save in any way.
The second hole contained a sign that said "a", as have I gotten AFK, i noticed it changed to "ab" mysteriously, maybe it's trying to convey a sentence?
Somehow I tried getting out of the second hole, but I had no jumping abilities for a while. Then I managed to get out.
The third hole DID contain something, but as soon I entered in something or someone covered the hole and I wasn't able to see anything in-game for 20 minutes. So I waited, and then it opened by itself mysteriously.
The fourth hole contained a sign which said "check". This is where I looked everywhere. And everywhere. Until I found something. Something I wasn't able to see, but I did it anyways. It was a person with a white skin, but all I know is that this world is singleplayer. There was no name and the only thing it said was "hide". Nothing else, then it left. Then all I knew was these holes were gone, mysteriously vanished.
After that I had a sense of paranoia. I may see something rather then nothing. But things just don't work out. I tried and tried several times, and it didn't work. Is this mystery even real? Who am I to know?
Minecraft is not safe. It never was.