Interesting. I have major low back problems... but my 2004 Outback seat gave me no issues whatsoever. My low back was supported nicely.
I have a 2008 Revolution I bought new and can usually only get about 4 hours before my back starts to ache.
I also have a 2015 Outback with the new seat and I have no problem staying out for much longer. I much prefer the new seat even though it is noisy.
I...can do long day after long day in my 2014 Revolution with no discomfort.
Each of you is using a different version of the Hobie seat.
Until 2007 models, Hobie used a flat back seat with broad, high back support. This was an excellent seat, but there was a bad batch that had aluminum staves instead of fiberglass. There were complaints but by the time Hobie recognized and corrected the problem, a new seat had been designed. This is my favorite seat (combined with the i-comfort seat described below) and I use it exclusively (bought some spares after production ceased).
2007 to 2009 models (version #2) is easily identified by being thicker and having a permanently inflated lumbar support. IMO this seat was the worst of all the designs -- poor back support, mandatory lumbar bulge!
2010 to 2014 models (version #3) was a great improvement over the previous version -- broader shoulder support higher up and a collapsible lumbar (air filled).
All of these versions had a small common problem for some of us -- the seat bottom could give you an achy butt after awhile. The (optional) i-comfort seat pad (introduced in 2008) is an excellent solution and well worth its price.
2015 models to current the Vantage chair seat seems to be very popular with most users. it's great number of adjustments (back, seat and lumbar), height adjustment and camp chair versatility mark a new era in seat design that can accommodate lots of shapes and sizes of users.