It says he went out with friends, saw movies, and even flew on planes while "frog-breathing", as he called it. He couldn't do it while unconscious so he still had to sleep in the lung.
So, to state it in computing terms, this wasn't a fix for not being able to breathe, it was a workaround. But it seems to have worked really well: at 40, he was "able to spend most of his day outside the machine that still kept him alive".
If this is reported correctly, it would even have been an deliberate choice to not leave more often or entirely.
EDIT: This was seemingly not reported correctly, it seems he only depended on the iron lung while sleeping but could otherwise live without it.
Contracting Covid, unfortunately. :(
Source: https://www.sueddeutsche.de/projekte/artikel/magazin/eiserne...
Source: https://www.nbcnews.com/news/us-news/paul-alexander-polio-su...