Little bit of difference there.  Self propelled J.D. swather's I've seen and been around don't have ADJUSTABLE throttles. You've got a toggle switch, idle and wide open.

The original poster was talking about Self propelled machines.

"Been cutting hay since I was 10, so I have a little experience in that regard."

ok so,, I too have been cutting hay that long myself. Started with a Model A and a 7 foot mower....

With a SELF PROPELLED swather, with speeding up the reel, most all of the crop can be picked up. I know since I've done it for years...

Didn't say sickle machines are 'plug proof' but the chances of plugging can be minimized with proper adjustments.