This legend was already going around college dorms in the late 1980s.
I heard it from older stoner-type kids while I was in high school in the early 90s in the pre-web. While not entirely possible, there is close to zero chance they heard it through digital means.
I hope we never get a definitive answer. I hope it stays a myth like the origin of "420".
Also, from the article:
Hardly anyone knew about it,
> In 1971, five high school students in San Rafael, California,[5][6] used the term "4:20" in connection with a plan to search for an abandoned cannabis crop, based on a treasure map made by the grower.[7][8] Calling themselves the Waldos,[9][10] because their typical hang-out spot "was a wall outside the school",[11] the five students—Steve Capper, Dave Reddix, Jeffrey Noel, Larry Schwartz, and Mark Gravich[12]—designated the Louis Pasteur statue[13] on the grounds of San Rafael High School as their meeting place, and 4:20 pm as their meeting time.[11] The Waldos referred to this plan with the phrase "4:20 Louis". After several failed attempts to find the crop, the group eventually shortened their phrase to "4:20", which ultimately evolved into a code-word the teens used to refer to consuming cannabis.[7]
Another San Rafael group claims to have originated the term before the Waldos
It was an urban legend. Slight disagreements about which lion roar to start the album on. Reasons why each song correlated to the events on screen, etc.
I thought there were some coincidences, but hardly worked as a soundtrack.
It totally works if you are super high.
It works though the same way that I will think I made some masterpiece of music while being super high and then when I listen the next day sober it is just 4 bars of total shit. It still sounded like a masterpiece in the moment. Marijuana is amazing at finding and grafting meaning on to things that aren't really there or just totally ordinary.
This legend was already going around college dorms in the late 1980s.
I don't know the origin either, but things spread by word of mouth in ways other than the internet. For example, I had friends who were Deadheads.