I've stated this before in a prior post but just in case you're new to the SCP Foundation: There is no single canon. Anyone can pick and choose what to accept and what not to accept as headcanon. Personally I believe this SCP-001 proposal (commonly referred to as "The Conspiracy") is one of several 001s that the SCP Foundation uses to mislead researchers in the Foundation when they go searching for the real SCP-001. The event this SCP proposal is based on is real though: The JFK assassination.

Image Source: White House Press Office (WHPO), public domain photo

SCP-001 in this proposal is the bullet that killed the 35th President of the United States. Was this bullet the third one that Lee Harvey Oswald fired at President John F. Kennedy? Yes. Was the same SCP-001 bullet fired by someone other than Lee Harvey Oswald? Again, yes. Multiple individuals shot the same bullet simultaneously according to the SCP file. SCP-001 is a kind of "magic bullet" and all the events involved in the SCP-001 bullet killing JFK are collectively designated by the Foundation as SCP-001-Gamma. SCP-001-Gamma would seem to have caused many historic events after the JFK assassination to be fluid. This is commonly referred to as the "Mandela effect".

How damaged is recorded history after the JFK assassination/Incident SCP-001-Gamma? In the video below at the 01:40 mark the date of the JFK assassination is stated to be November 22nd, 1963. At the video's 04:01 mark the date is given as November 22nd, 1969. Was it in 1963 or four months after the first man stepped on the Moon? Pick a year SCP Explained - Story & Animation YouTube channel!

I am suspicious of this proposal being a real SCP-001 for two main reasons. First, this proposal seems too similar to the established SCP-2001 effect. Basing a false SCP on a real SCP would make the false SCP seem bona fide. Second, the claim of a "shared concept of truth" prior to 11/22/1963 doesn't seem legit to me. Let's be honest; using three pounds of meat as memory storage isn't ideal. The "Mandela effect" is just people misremembering information. Many people incorrectly remember the Berenstain Bears series as the "Berenstein Bears", the first book in the series published a year prior to JFK getting shot. Another pre-1963 "Mandela effect" often cited is "Mirror, mirror, on the wall... " from a 1937 Disney movie. If SCP-001-Gamma is real then why doesn't the SCP Foundation file describe the retroactive affects to history as well?

If this SCP-001 proposal isn't a real SCP then SCP-3780 is most likely also a red herring. I like the movie Running Against Time but did the SCP Foundation really need to make the movie's premise an SCP?