I don't disbelieve that this event happened, but when we're trying to verify the origin of people saying a catchphrase, pointing to a single example of someone saying it is poor evidence, even if it was a notable or especially funny example.
We need more than a funny example of someone saying "Orb," because that could have been done as part of the tradition.
When I search for this runner's speedruns, all of the oldest ones were done in 2015. That's also when he joined https://speedrun.com (profile IsoFrieze).
But "orb" is from 2013 or earlier, as you'll soon see. Again, the claim isn't disproven. That runner joined Twitch in April of 2013 as profile IsoFrieze, but profile dotsarecool has been deleted. The event could have happened on the other account, or before he got any upload-worthy runs.
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When I search for this runner's speedruns, all of the oldest ones were done in 2015. That's also when he joined https://speedrun.com (profile IsoFrieze).
He has some comments on Reddit about SMW glitch chasing from 2014. Comments from before that are not SMW related.
Again, not disproven, but no real evidence to back it up.