Enevhar Aldarion
Hero
Or he was faking it in the hope that his superiors wouldn't be aware he'd dosed himself. Otherwise he'd have to expect his "non-honorable" discharge to come with a side-order of enforced hospitalisation and medical examinations.
I had to go and read a little on Steve's healing ability too and it generally says he can fully heal broken bones in days, rather than weeks or months. So depending on how quickly that court martial was set up, Walker's arm could be healing at the same rate that Rogers would have, but it was just not fully healed yet.