You send them your 2nd rings out of a standard Lycoming or Superior set and they grind them for the gapless ring. They send you the rings back with matched rails.
If the top ring seals too well the 2nd ring won't, unless its an extreme application such as a drag motor. Due to insufficient gas pressures at the 2nd ring in that case. The cylinder pressures aren't high enough in a Lycoming to make two gapless rings effective.
No groove turning is required if they modify stock rings.
If you use their rings then a square ring groove is required.
Talk to Keith at Totalseal. When I asked what grit of honing stone to use he said 280 and that's what Lycoming and Continental spec.