There is a cagillion ways to skin a cat. Form tool is for consistancy and speed cutting rims reguardless of method. The main benefit of keeping the mandrel and form tool in a stationary state is consistancy with rim face. Cuz it locates off the rim face and it doesn't matter about case length even changing from 22-250 to 308 all rims will be the same. Once set only an in out cutting movement is needed. (same primer pocket only).
1BG I am going to guess your question is about what keeps the rim from spinning when the tool makes contact? That where the stippling comes in. It is simular to knurl but is done with a sharp punch on mandrel face where it drives rim face. Combined with tailstock pressure allows the mandrel to grab/dig into the face. Using this method you will get the "FEEL" of how fast to feed the tool and how much pressure is needed to prevent case slippage. When setup there is no need to stop spindle as left hand inserts case while righthand tightens talestock. Left hand turns cross slide while pressure is applied by right hand on tailstock ("FEEL"). Right hand loosens talestock an left removes finish rebated casing. REPEAT.
The drill press method would require a fixture with a bearing that the mandrel would be mounted, inline with the spindle. (Bolted to drill press table). A brazed on carbide square shank form tool would be needed. Tool would be set in a slot in fixture milled at tangent or slightly below centerline. Method#1 For feeding the tool in and out a fine pitch screw (8-40?)could be used by tapping a hole into end of tool and rigging up tool stops, feed knob, etc hardware. Method#2 A lever could be mounted and a spring used for dampining to slow feed. For driving this mess, an internal mandrel would be need with a rubber or urethane to spin the brass via the case shoulder. Using the left/right hand method above no stopping of spindle to tighten or losen anything would be needed. This fixture has the same idea of consistant tool to rim face idea. Case length doesn't matter.
I agree BFD if your making 50 cases it's not worth while but 1BG idea of multicaliber AK combined with a rifle that will throw brass would equal a LOT of cases. There is no glory in turning rims.