It's all talk. POTUS cannot reverse or remove pardons from other presidents.
A sitting U.S. president cannot revoke or remove a pardon granted by a previous president. Once a pardon is issued and accepted, it is considered final and cannot be undone by a future administration. This is because a presidential pardon is a constitutional power under Article II, Section 2 of the U.S. Constitution, and once granted, it is legally binding. Courts have generally held that a pardon, once delivered and accepted, cannot be rescinded by any subsequent president. However, a new president could pursue other legal avenues, such as reopening investigations or bringing new charges for separate offenses not covered by the original pardon.