Still not sure if I understand right.
                                                                                    The report was released to the public on the 26th.
                                                                                    But.
                                                                                    
Aug. 12 — A 
whistleblower files a complaint, addressed to chairmen of the House and Senate intelligence committees, that says: “In the course of my official duties, I have  received information from multiple U.S. Government officials that the  President of the United States is using the power of his office to  solicit interference from a foreign country in the 2020 U.S. election.” 
                                                                                    Then:  
Aug. 26 — 
Michael Atkinson, the inspector general for the intelligence community, 
writes  to Acting Director of National Intelligence Joseph Maguire to say that  he has reviewed the whistleblower’s complaint and has deemed it an  “‘urgent concern’ that ‘appears credible.'” Atkinson informs Maguire  that, under the law, he has seven days to forward the complaint to the  committee chairmen “together with any comments the Director considers  appropriate.”
                                                                                    
Sept. 9 — Atkinson, the inspector general of the intelligence community, 
notifies  the House intelligence committee that he received a whistleblower’s  complaint relating to an “urgent concern” on Aug. 12. He says he found  the information credible, and sent “my determination of a credible  urgent concern” along with a copy of the complaint to Acting Director of  National Intelligence Joseph Maguire, who had seven days to forward the  complaint to Congress. But, contrary to “past practice,” Maguire did  not forward the complaint to Congress, believing “the allegations do not  meet the definition of an ‘urgent concern’ under the [whistleblower]  statute,” Atkinson writes. The inspector general says he will keep the  committee apprised of his attempts to resolve the issue.
                                                                                    Three House committees 
announce investigations  into whether Trump and Giuliani tried to pressure Ukraine into  conducting “politically-motivated investigations under the guise of  anti-corruption activity.”
                                                                                    
Sept. 13 — Democratic Rep. Adam Schiff, the chairman of the House intelligence committee, 
issues  “a subpoena to the Acting Director of National Intelligence (DNI)  Joseph Maguire to compel the production of a whistleblower complaint  that the Intelligence Community Inspector General’s (IC IG) determined  to be credible and a matter of ‘urgent concern,’ as well as the IC IG’s  determination and all records pertaining to the Office of the Director  of National Intelligence’s (ODNI) involvement in this matter, including  any and all correspondence with other Executive Branch actors such as  the White House.”
                                                                                    
Sept. 18 — The 
Washington Post, citing unnamed sources, 
reports  that the whistleblower complaint involves Trump’s “communications with a  foreign leader,” including “a ‘promise’ that was regarded as so  troubling that it prompted an official in the U.S. intelligence  community to file a formal whistleblower complaint.”
                                                                                    So in all of this, if we're talking 'leak' as in when the committee's were first aware, it was at the earliest August.  If we're talking leak as in got out to the public, then it's the 18th.
                                                                                    This is using your own link.
                                                                                    So Pelosi announces on the 24th that they're going through with the impeachment inquiry.
                                                                                    Which is after all this happened.
                                                                                    Pelosi had no choice at this point but to go forward with it.