And those 32" barrels are probably getting less than 100 fps over a 22" barrel. So yes "longer is not better all the time". It is only better in very rare circumstances and even in this case you'd be much better off with another chambering rather than havng to resort to such extreme barrel lengths.
A barrel of 18-22" does about all 99% of the folks who use a 308 needs to do. Just my personal feelings, but I don't like to go under 20" and feel anythng over 22" is a waste in a 308. It is more about how the gun balances and handles as well as muzzle blast than bullet speed. I'd hunt any animal in North America with a 20" 308 and feel good about taking all but the big bears out to 400 yards. I'd limit shots on the huge stuff to under 100.