According to the SEC release. They may have set that number based on their own assumptions of their ability to complete the filing, but the release explicitly states that the company window is 45 days.
References:
1. 17 CFR § 230.257(f) - Periodic and current reporting; exit report, states, “An issuer that is not able to meet a filing deadline for any report or form required to be filed by § 230.252(f)(2)(i) or paragraphs (a) through (c) of this section during the period from and including March 26, 2020, to May 31, 2020, due to circumstances relating to coronavirus disease 2019 (COVID-19) shall be deemed to have satisfied the filing deadline for such report or form if:
(i) The issuer promptly discloses on its public website or provides direct notification to its investors that it is relying on this paragraph (f); and
(ii) The issuer files such report or form with the Commission no later than 45 days after the original filing deadline of the report or form.
In any report or form filed pursuant to paragraph (f)(1)(ii) of this section, the issuer must disclose that it is relying on this paragraph (f) and state the reasons why, in good faith, it could not file such report or form on a timely basis.
2. SEC Release No. 34.88465, 25 March, 2020 states, “On March 4, 2020, in response to the potential effects of coronavirus disease 2019 (COVID-19), the Securities and Exchange Commission (the “Commission”) issued an order (the “Original Order”) pursuant to its authority under Section 36 of the Securities Exchange Act of 1934 (the “Exchange Act”) granting exemptions from certain provisions of that Act and the rules thereunder related to the reporting and proxy delivery requirements for certain public companies, subject to certain conditions. The Commission has been monitoring the effects of COVID-19 and is now modifying the exemptions in light of its current understanding of the circumstances. The health and safety of all participants in the securities markets is of paramount importance, and the Commission recognizes that public companies and other market participants continue to face challenges in meeting the reporting and proxy delivery requirements of the federal securities laws in a timely manner. For this reason and the reasons stated in the Original Order, the Commission finds that modifying the exemptions to cover filings due on or before July 1, 2020, pursuant to its authority under Section 36 the Exchange Act, is appropriate in the public interest and consistent with the protection of investors. This Order supersedes the Original Order.”
3. SEC Release No. 34.88318 (Section II), dated 4 March, 2020 states, “Disruptions to transportation, and limited access to facilities, support staff, and professional advisors as a result of COVID-19, could hamper the efforts of public companies and other persons with filing obligations to meet their filing deadlines. At the same time, investors have an interest in the timely availability of required information about these companies and the activities of persons required to file schedules and reports with respect to these companies. While the Commission believes that the relief from filing requirements provided by the exemption below is necessary and appropriate in the public interest and consistent with the protection of investors, we remind public companies and other persons who are the subjects of this Order to continue to evaluate their obligations to make materially accurate and complete disclosures in accordance with the federal securities laws.”
