This is one of the things I like about my software (UltraTax). Below is an excerpt from the template Filing Instructions that is automatically generated for each return I file. It is a concise and accurate description of what is actually happening. I find that many people do not know that they are actually signing their efiled federal tax return with a PIN.

"You have already signed Form 8879 IRS e-file Signature Authorization. Your signature
authorizes your electronically filed return to be signed with a Personal Identification Number
(PIN), and indicates your agreement that the Part I amounts are from your tax return. No further
signature action is required.​"