I suppose this is analogous to how physical postmarks are accepted by the IRS.  If the return is filed late and postmarked by USPS on Christmas eve but not delivered to the IRS until after the holiday, the IRS would only take the date of delivery as the filing date.  See also this article from the IRS: https://www.irs.gov/e-file-providers/electronic-postmark

Ditto on whether Intuit actually accepted returns for submission after their self-imposed cutoff before 11:59pm.