Some are absolutely unable to return to work, they know that, and struggle to understand what they must do to secure benefits.
An aside, this just reminded me of that nightmare period leading up to finishing work, it was a period of not knowing whether I would get any pension, whether I would be able to afford continuing living my own home or if I would end up having to move in with family at the other end of the country. This was a number of years post onset, and a number of years after having reduced to part time working.
Some of this uncertainty reflected my lack of knowledge what was possible, what the system is, but most of the uncertainty was around not knowing how the various systems will respond to ME (or Long Covid), or indeed if they would recognise it at all in your case.
An ideal system for the specific needs of our condition would allow much freer movement between working and not working and between either to working reduced hours. And it would not be a system with such a high energy costs in achieving and sustaining pensions/benefits. I feel a system that would allow people to withdraw from work sooner, but be able to return to part time work more easily, and yet again withdraw from work if necessary, according to current health needs might end up with better health outcomes and people working more overall.
This paper draws on an ideological assumption that working is good, not working is bad, whereas for some people with Long Covid not working will be inevitable, and the fight to continuing full time work may actually lead to worse health outcomes. There is the possibility that encouraging people to stop work sooner, with mechanisms for future part time working or phased return to work may produce better long term outcomes.
We need a system that recognises this may be a life long condition and considers setting up options for the decades ahead, not just answering the question is it back to full time work or deciding never to work again in the next few months.
[added - such flexibility may be impossible to achieve within our current adversarial benefits systems]