Enlargements of the (relatively) recently discovered "studio" portrait of Patton, clearly shows him playing "knife" style on a "12 fret" parlour held at 45 degrees on his lap.
Further evidence in favour of Patton's use of "knife" style, comes from recordings like "When Your Way Gets Dark", played in open A, which features regular slide excursions up to the 17th fret (assuming he was tuned 'up' to open A, or the 19th fret, if he was tuned 'down' to open G and capoed at the 2nd fret), which are hardly easy to play "bottleneck" style. This lick found it's way into Robert Johnson's "Come On In My Kitchen".
Both Patton and Johnson also often tended to play slide out of 'Spanish' tuning pitched in keys as high as B and B flat.
We tend to forget that pre-war steel string sets came in just one gauge: 14 to 64. Prior to the mid-'30s, guitars had no adjustable truss rods and only a few, top-of-the-line, instruments even had an inert truss rod.
Cheaper instruments within the financial reach of blues players would not have been able to take the string tension of a set of steel strings tuned to open A without exploding.
Just in standard tuning, a string set like this tuned to concert on a guitar with a 24.8" scale, generates 220 lb ft of torque on a guitar bridge. That's probably more than the peak torque your car puts down to the road through its driven wheels.
Skip James recorded using a Stella 12 string, strung with only 6 strings and tuned down to "cross note" 3 frets below concert.
I suspect everyone else tuned down and used a capo. Try playing bottleneck on a "12 fret", tuned to open G and capoed at the 4th fret to play in the key of B. What used to be your 12th fret is now fret 16. Now play that Patton lick that used to go to fret 17, but which now goes from fret 16 to fret 21. Easy, isn't it?
Now forget about "bottleneck" and play it "knife" style, as I'm convinced they did, back in the day.