I don't mean to be a jerk or anything, but from your replies, I don't think you understand what that word means. If you did, you would realize the statement is false.
Something only sets a precedent if subsequent decisions (of a kind) follow the initial one. For example, George Washington did not run for a 3rd term as US President. Neither did Thomas Jefferson, James Madison, Monroe, Jackson, Grant, Cleveland, or Wilson. Washington set a precedent that held until FDR, 130+ years later.
But you cannot say it was precedent setting BEFORE Jefferson's decision not to run for a 3rd term. That is where we are here. Sort of.
For a fact, no subsequent show has been cancelled after 3 seasons. So no precedent has been set.
In fact, factually, one can argue it DIDN'T set a precedent. The decision for Picard to run only 3 seasons was made at the outset. I may be confused on the dates, but it premiered in 2020, the decision had to be 2019 (or sooner). Disco was renewed for S4 in August of 2021. After they knew Picard was 3 seasons. Disco was renewed for season 5 in Jan of 2022. They were CONFIRMING S3 as the last for Picard the same week (decision made earlier).
Further, LD was also renewed for S4 in Jan of 2022. And for S5 in March of 2023.
That's 4 renewals, 2 DISCO and 2 LD, of 2 different series, both going beyond S3, since the decision to end Picard at S3 was made. And the number of series that have been stopped at 3 since? Zero.
That is the opposite of precedent.