With a line spool holder and a hand cranking device, line is wound directly onto a detached spinning reel spool. The line goes on the spool without any twist. As a result, line on the spool tends to stay put. But each revolution of the line as it leaves the spool during a cast puts a full twist into the line between lure and rod. Twisted line can interfere with contact with lures, reduce sensitivity to light strikes, and tangle the rod tip, particularly if the monofilament is stiff and has a strong memory that retains both the line twist and spool shape.
Line is taken directly off the supply spool by winding the reel handle.
The line twists once for each turn of the reel handle as it goes on the spool, unless you have one of the new twistless or twist-reducing rollers. In the early days of spin-fishing, when all monofilament lines were stiff, springy, and had strong memories, the twisted line on the spool created major problems. It seemed to spring up constantly, and was almost impossible to fish with. Tangles were frequent whenever baits were retrieved under light tension and line was loosely respooled. But, when cast, the line untwisted and the angler had a more direct contact with baits or lures.