The Constitution doesn’t even require that the pardon be written, so the idea that the signature is by autopen rather than by handwritten signature is not relevant to the constitutionality because Article II just says that the President has the power to pardon. Shit you can ask Biden today if he pardoned them.
Article II, Section 2, Clause 1:
The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States; he may require the Opinion, in writing, of the principal Officer in each of the executive Departments, upon any Subject relating to the Duties of their respective Offices, and he shall have Power to grant Reprieves and Pardons for Offences against the United States, except in Cases of Impeachment.
Listen Nostradumbass... You are a dumbass.