any single-pivot bike is a crap climber unless you lock it out, which defeats the object really.
Have you actually ever ridden a single pivot, or is that just an 'internet fact'?
My Rush climbs as well as any other full-sus I've ever ridden.
Then you need to ride more full-sus's 😉
I have owned a 2008 rush and it was frankly crap at climbing. There is a reason why most manufacturers have moved away from SP designs, they are simply too prone to bobbing all over the place. Ride a modern marin or whyte design (a company now sworn away from SP) and notice the actual ability to tackle technical climbs .. whilst sat down .. with the suspension still working! If you lock/pro-pedal a shock then you are simply stopping the design 'working' and you'll just slow yourself down as the rear wheel stutters and smacks into roots and rocks that the suspension should be dealing with.
How many professional XC riders do you see rocking a SP bike? hmmm. SP translates to fun, hooligan bikes – like Orange produces. Nowt wrong with that but if you want genuine versatility look at something like a Trek EX or Whyte e120.
I have worked in bike retail for many years and test ridden many many bikes, but these are simply my subjective thoughts and experiences.