If you suffer from lumbar (or any other region) pain in your column, reclining or not is a huge difference. I never had problems about knees getting closer or not, etc., but having suffered from lumbar pain for a part of my life, I can assure you that reclining or not has a big impact. No, it doesn't mean that pain -> need to recline. Sometimes it gets better keeping it straight, sometimes you get relief when you rec…
But other people do, that's the point.
I'm only 6'1 but with long legs, if someone reclines in front they're literally on top of my knees the entire flight. When turbulence occurs they bounce up and down on my knees.
I try to book exit rows and Economy+ when budget allows, but for all other times I take painkillers and just have to let my knees get damaged by the 4' woman in front of me who's comfort is more important than my pain.