Excellent points. Jesus directed Judas to betray him too, but he didn't repent like Peter did.
One cannot "receive" something unless they "accept" it, which implies willingness. Thus, the mark is not forced, though there may be various levels of persuasion used. Ultimately, those that receive the mark do so of their own free will.
They will be given a "choice" to take the mark or not, to live or die based on that.They spoke the words. The option would have been to not speak. They chose to speak. Yes, they were pressured, but they still chose to speak.
"Do not be afraid of those who kill the body but cannot kill the soul. Rather, be afraid of the One who can destroy both soul and body in hell" (Matt. 10:28).
Having said that, I think Centanni and Wiig are ok. They were released and have had time to renounce what they 'chose to do' under extreme pressure.
BUT, I think the real thing to take away from this is WHAT IF THEY HAD BEEN BEHEADED IMMEDIATELY AFTER THEY SPOKE THE LAST WORDS OF THEIR 'CONVERSION'? What if they had no opportunity to recant or repent?